do an full

7/31/2019 do an full

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CHNG I: TNG QUAN V CC H THNG

THNG TIN DI NG TH H 3

Chng I gii thiu mt cch tng quan v h thng thng tin di ng th h 3,

chin lc dch chuyn t h thng GSM ln h thng UMTS. T gip chng ta

hiu c kin trc c bn ca h thng thng tin di ng UMTS cng nh h thng h

thng thng tin di ng WCDMA/UMTS.

1.1 L trnh pht trin thng tin di ng ln 4G

L trnh pht trin cc cng nghthng tin di ng ln 4G c cho trn hnh 1.1

Hnh 1.1: L trnh pht trin cc cng nghthng tin di ng ln 4


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H thng di ng th h 1 ch h trcc dch v thoi tng t v s dng k

thut iu chtng t mang d liu thoi ca mi ngi, v s dng phng php

a truy nhp phn chia theo tn s FDMA.H thng thng tin di ng th h2 c a ra p ng kp thi slng ln

cc thu bao di ng da trn cng ngh s. Tt c h thng thng tin di ng th h 2

u s dng iu ch s. V chng s dng 2 phng php a truy cp l :

- a truy cp phn chia theo thi gian (TDMA).

- a truy cp phn chia theo m (CDMA).

H thng thng tin di ng chuyn t th h 2 sang th h 3 qua mt giai on

trung gian l th h 2,5 s dng cng nghTDMA trong kt hp nhiu khe hoc

nhiu tn s hoc s dng cng nghCDMA trong c th chng ln ph tn ca th

h hai nu khng s dng ph tn mi, bao gm cc mng c a vo s dng

nh: GPRS, EDGE v CDMA2000-1x. th h th 3 ny cc h thng thng tin di

ng c xu th ho nhp thnh mt tiu chun duy nht v c khnng phc vtc

bit ln n 2 Mbit/s. phn bit vi cc h thng thng tin di ng bng hp hin

nay, cc h thng thng tin di ng th h 3 gi l cc h thng thng tin di ng bng

rng.

H thng thng tin di ng th h 3 sang th h4 qua giai on trung gian l th

h 3,5 c tn l mng truy nhp gi ng xung tc cao HSDPA. Th h 4 l cng

ngh truyn thng khng dy tht, cho php truyn ti d liu vi tc ti a trong

iu kin l tng ln ti 1 cho n 1.5 Gb/giy. Cng ngh4G c hiu l chun

tng lai ca cc thit b khng dy. Cc nghin cu u tin ca NTT DoCoMo cho

bit, in thoi 4G c th nhn d liu vi tc 100 Mb/giy khi di chuyn v ti 1

Gb/giy khi ng yn, cho php ngi s dng c th ti v truyn ln hnh nh ng

cht lng cao. Chun 4G cho php truyn cc ng dng phng tin truyn thng ph

bin nht, gp phn to nn nhng ng dng mnh m cho cc mng khng dy ni b

(WLAN) v cc ng dng khc.
http://vi.wikipedia.org/w/index.php?title=%C4%90i%E1%BB%81u_ki%E1%BB%87n_l%C3%BD_t%C6%B0%E1%BB%9Fng&action=edithttp://vi.wikipedia.org/w/index.php?title=%C4%90i%E1%BB%81u_ki%E1%BB%87n_l%C3%BD_t%C6%B0%E1%BB%9Fng&action=edithttp://vi.wikipedia.org/w/index.php?title=%C4%90i%E1%BB%81u_ki%E1%BB%87n_l%C3%BD_t%C6%B0%E1%BB%9Fng&action=edithttp://vi.wikipedia.org/w/index.php?title=%C4%90i%E1%BB%81u_ki%E1%BB%87n_l%C3%BD_t%C6%B0%E1%BB%9Fng&action=edithttp://vi.wikipedia.org/w/index.php?title=%C4%90i%E1%BB%81u_ki%E1%BB%87n_l%C3%BD_t%C6%B0%E1%BB%9Fng&action=edithttp://vi.wikipedia.org/w/index.php?title=%C4%90i%E1%BB%81u_ki%E1%BB%87n_l%C3%BD_t%C6%B0%E1%BB%9Fng&action=edithttp://vi.wikipedia.org/wiki/NTT_DoCoMohttp://vi.wikipedia.org/wiki/Gigabytehttp://vi.wikipedia.org/wiki/Gi%C3%83%C2%A2yhttp://vi.wikipedia.org/wiki/Gi%C3%83%C2%A2yhttp://vi.wikipedia.org/wiki/Gigabytehttp://vi.wikipedia.org/wiki/NTT_DoCoMohttp://vi.wikipedia.org/w/index.php?title=%C4%90i%E1%BB%81u_ki%E1%BB%87n_l%C3%BD_t%C6%B0%E1%BB%9Fng&action=edit


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Th hdi ng 4G dng k thut truyn ti truy cp phn chia theo tn s trc

giao OFDM, l k thut nhiu tn hiu c gi i cng mt lc nhng trn nhng tn

s khc nhau. Trong k thut OFDM, ch c mt thit b truyn tn hiu trn nhiu tnsc lp (t vi chc cho n vi ngn tn s).

Hnh 1.2: Ltrnh tng tc truyn s liu trong cc pht hnh ca 3GPP

Trn y l ltrnh tng tc truyn s liu trong cc pht hnh ca 3GPP tri

qua cc giai on tR3 n R8.

1.2 Kin trc chung ca mt h thng thng tin di ng 3G

Mng thng tin di ng 3G lc u s l mng kt hp gia cc vng chuyn

mch gi v chuyn mch knh truyn s liu gi v ting.

Cc vng chuyn mch knh (CS) v chuyn mch gi (PS) c th hin bng

mt nhm cc n v chc nng lgic: trong thc hin thc t cc vng chc nng nyc t vo cc thit b v cc nt vt l. Chng hn c th thc hin chc nng

chuyn mch knh CS (MSC/GMSC) v chc nng chuyn mch gi (SGSN/GGSN)

trong mt nt duy nht c mt h thng tch hp cho php chuyn mch v


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truyn dn cc kiu phng tin khc nhau: t lu lng ting n lu lng s liu

dung lng ln.

3G UMTS (Universal Mobile Telecommunications System: H thng thng tin ding ton cu) c th s dng hai kiu RAN :

Kiu th nht s dng cng ngh a truy nhp WCDMA (Wide Band CodeDevision Multiple Acces) c gi l UTRAN (UMTS Terrestrial Radio Network)

mng truy nhp v tuyn mt t ca UMTS.

Kiu th hai s dng cng ngh a truy nhp TDMA c gi l GERAN(GSM EDGE Radio Access Network) mng truy nhp v tuyn da trn cng ngh

EDGE ca GSM.

Cc trung tm chuyn mch gi s l cc chuyn mch s dng cng ngh ATM.

Trn ng pht trin n mng ton IP, chuyn mch knh s dn c chuyn sang

chuyn mch gi. Cc dch v k c s liu ln thi gian thc ( nh ting v video )

cui cng sc truyn trn cng mt mi trng IP bng cc chuyn mch gi.

Hnh 1.3: Kin trc chung ca mng thng tin di ng 3G


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1.3 Cu trc mng 3GWCDMA

H thng W-CDMA c xy dng trn c smng GPRS.V mt chc nng c th chia cu trc mng W-CDMA ra lm hai phn: Mng

li (CN) v mng truy nhp v tuyn (UTRAN). Trong mng li s dng ton b

cu trc phn cng ca mng GPRS cn mng truy nhp v tuyn l phn nng cp ca

W-CDMA.

Ngoi ra hon thin h thng, trong W-CDMA cn c thit bngi s dng

(UE) thc hin giao din ngi s dng vi h thng.Tquan im chun ha, c UE

v UTRAN u bao gm nhng giao thc mi c thit k da trn cng ngh v

tuyn W-CDMA, tri li mng li c nh ngha hon ton da trn GSM. iu ny

cho php h thng W-CDMA pht trin mang tnh ton cu trn cscng ngh GSM.

Hnh 1.4: Cu trc UMTS


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UE (User Equipment)Thit bngi s dng thc hin chc nng giao tip ngi s dng vi h thng.

UE gm hai phn :Thit b di ng ME : L u cui v tuyn c s dng cho thng tin v

tuyn trn giao din Uu.

Module nhn dng thu bao UMTS (USIM) : L mt th thng minh cha thngtin nhn dng ca thu bao, n thc hin cc thut ton nhn thc, lu gi cc kha

nhn thc v mt s thng tin thu bao cn thit cho u cui.

UTRAN (UMTS Terestrial Radio Access Network)Mng truy nhp v tuyn c nhim v thc hin cc chc nng lin quan n truy

nhp v tuyn. UTRAN gm hai phn t :

Nt B : Thc hin chuyn i dng s liu gia cc giao din Iub v Uu. N cngtham gia qun l ti nguyn v tuyn.

Biu khin mng v tuyn RNC : C chc nng shu v iu khin cc tinguyn v tuyn trong vng (cc nt B c kt ni vi n). RNC cn l im truy

cp tt c cc dch v do UTRAN cung cp cho mng li CN.

CN (Core Network)HLR (Home Location Register) : L thanh ghi nh vthng tr lu gi thng

tin chnh v l lch dch v ca ngi s dng. Cc thng tin ny bao gm :

Cc dch vc php, cc vng khng c chuyn mng . Cc thng tin v dch v bsung nh : trng thi chuyn hng cuc gi,

s ln chuyn hng cuc gi.

MSC/VLR: L tng i (MSC) v c sd liu (VLR) cung cp cc dch vchuyn mch knh cho UE ti v tr ca n. MSC c chc nng s dng cc giao dch

chuyn mch knh. VLR c chc nng lu gi bn sao v l lch ngi s dng cng

nh v tr chnh xc ca UE trong h thng ang phc v.

GMSC (Gateway MSC) : Chuyn mch kt ni vi mng ngoi.


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SGSN (Serving GPRS) : C chc nng nh MSC/VLR nhng c s dng chocc dch v chuyn mch gi (PS).

GGSN (Gateway GPRS Support Node) : C chc nng nh GMSC nhng chphc v cho cc dch v chuyn mch gi.

Cc mng ngoiMng CS : Mng kt ni cho cc dch v chuyn mch knh.Mng PS : Mng kt ni cho cc dch v chuyn mch gi.Cc giao din v tuynGiao din CU : L giao din gia th thng minh USIM v ME. Giao din ny

tun theo mt khun dng chun cho cc th thng minh.

Giao din UU : L giao din m qua UE truy cp cc phn t cnh ca hthng v v th m n l giao din mquan trng nht ca UMTS.

Giao din IU : Giao din ny ni UTRAN vi CN, n cung cp cho cc nh khaithc khnng trang b UTRAN v CN t cc nh sn xut khc nhau.

Giao din IUr : Cho php chuyn giao mm gia cc RNC t cc nh sn xutkhc nhau.

Giao din IUb : Giao din cho php kt ni mt nt B vi mt RNC. IUbctiu chun ha nh l mt giao din mhon ton.

1.3.1 Kin trc 3G WCDMA/UMTS R3

V giao din v tuyn:

Phn mng truy nhp v tuyn mi UTRAN ( WCDMA ) c thm cc thnhphn RNC v BC.

Vic c nng cp giao din v tuyn hin c ca GSM ln EDGE (E-RAN) haykhng l ty chn ca nh khai thc.


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MSC/VLR nng cp c th xl c cho phn v tuyn bng rng.

cc dch v IN c th cung cp cho cc mng tm tr ca thu bao cn trin

khai CAMEL.Kt ni truyn dn trong mng truy nhp v tuyn WCDMA dng cng ngh

ATM nhm h trcc loi hnh dch v khc nhau: cc dch v tc khng i cho

chuyn mch knh v v cc dch v c tc thay i i vi chuyn mch gi.

Cc nt li c chuyn i:

Phn CS phi qun l cthu bao 2G v 3G, i hi thay i trong MSC/VLRv HLR/AuC/EIR.

Phn PS c nng cp tGPRS, thay i SGSN l ln nht.Mng cung cp cc loi dch v 3G v dch v ging vi mng 2.5G, hu ht cc

dch vc chuyn sang dng gi khi c nhu cu. V d WAP s chuyn sang dng

chuyn mch gi. Dch v da trn v tr gip truyn d liu gi hiu quhn.

Hnh 1.5: M hnh 3G WCDMA/UMTS R3

u im:

Tn dng ti a h tng GSM/GPRS hin c:


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C th trin khai nhanh chng. Ch tiu cc phn t mng rt n nh.Cung cp c dch v 2G v 3G, dch v chuyn mch knh v gi.Bo m an ton u t:Thit b nng cp dn dn ti mng li 3G.

Nhc im:

Phc tp do c hai thnh phn CS v PS.Phn CS phc tp do phi phc v c 2G v 3G, kh mrng.Vic qun l h thng s phc tp.


Hnh 1.6: Kin trc 3G WCDMA/UMTS R4


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im khc bit chnh ca pht hnh 4 v pht hnh 99 l mng li phn b. MSC

c chia thnh MSC sever v MGW. 3GPP pht hnh 4 tch phn kt ni, iu khin

v dch v cho chuyn mch knh mng li.MSC sever c chc nng qun l di ng v iu khin cuc gi, khng cha

ma trn chuyn mch, phn tiu khin MGW.

Media Gateway (MGW) l phn t chiu trch nhim duy tr cc kt ni v thchin chc nng chuyn mch khi cn.

Thoi chuyn mch gi (VoIP): cuc gi chuyn mch knh c chuyn sangchuyn mch gi trong MGW.

u im:

Khc phc mt snhc im ca R99.Tch ring phn kt ni cuc gi, phn iu khin v phn dch v cho phn

chuyn mch li chuyn mch knh.

Ton b lu lng qua MGW, c qun l nng MSC Sever tch ri ( nngcp t MSC/VLR).

Phn CN CS c th t do mrng khi dung nhiu MGW.Cho php truyn ti lu lng hiu quhn nhchuyn mch gi. Mt cuc gi

GSM truyn thng s c thay bng VoIP qua MGW. Phn h a phng tin

IP(IMS) c thm vo p ng cc dch va phng tin trn IP v VoIP.

Nhc im:

Lm thay i cn bn phn CS nhng vn cn c hai thnh phn CS v PS.Vai tr ca CAMEL sthay i, phi lp kt ni vi phn PS v s trthnh yu

tu ni gia h tng dch v v mng.


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c im ca mng 3G pht hnh 5 l thm min IP a phng tin trong mngli, h trd liu v thoi qua IP, trong b sung mt s phn t mi:

CSCF: Qun l vic thit lp duy tr v gii phng cc phin truyn aphng tin vi ngi s dng.

MRF: H trcc chc nng nh cuc gi nhiu bn, cuc gi hi ngh.Ngoi ra, SGSN v GGSN c ci tin so vi R4 l c h trthoi.

MGW vn c chc nng tng tnh R4 v MGW do MGCF iu khin.

Hnh 1.7: Kin trc 3G WCDMA/UMTS R5

u im :

Tn ti duy nht chuyn mch gi PS.


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S dng hiu qu v d dng qun l ton blu lng trn mng 3G v u lIP.

Cng ngh truy nhp v tuyn s gim dn t trng. Trong tng lai, cc li 3Gs c nhiu cng ngh truy nhp v tuyn khc nhau.


Mc ch chun ha ca 3GPP Relesae 6 l:

Cung cp cc dch va phng tin IP, pha 2: Nhn tin IMS v qun l nhm.Hot ng phi hp vi mng LAN v tuyn.Cc dch v ging ni: Nhn dng ging ni phn b (DSsR).Phm vi v nh ngha ang tip tc c tiu chun ha

1.4 Cc knh c bn ca WCDMA/UMTS

Hnh 1.8: Cu trc knh c bn ca WCDMA/UMTS


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Trong W-CDMA c 3 nhm knh c bn:

Knh logicKnh truyn tiKnh vt lKnh logic:

Miu t loi thng tin sc truyn i. Mc d gi l "knh" nhng n khng

phi l knh theo ging ngha nh knh vt l, knh vn ti. Knh logic c th hiu l

nhng cng vic m mng v thit b cn phi thc hin ti nhng thi im khc

nhau.Cc knh logic ny cng c thxem nh l dch v m lp MAC cung cp cho

lp RLC trn n.

Knh vn ti:

Qui nh bng cch no v vi c trng g thng tin sc truyn i.y l

dch v m lp vt l cung cp cho lpMAC trn n.

Knh vt l:

L knh hin hu truyn ti thng tin i.

Vic phn ra cc loi knh khc nhau mnh ngh l ging vic phn lp trong

mng, gip cho d qun l v iu khin. C ng vi mi loi thng tin km theo

nhng c trng ca n, mng s t ng truy cp vo cc knh tng ng gi

thng tin i mt cch hiu qu nht.

1.4.1 Knh logic

Knh logic nh ngha loi s liu c truyn i, bao gm 2 loi knh: Knh

iu khin v knh lu lng.
http://tudiencongnghe.com/Special:Search/MAChttp://tudiencongnghe.com/Special:Search/MAC


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Hnh 1.9: Cu trc knh logic

1.4.1.1 Knh iu khin

Knh iu khin chungKnh iu khin qung b (BCCH): hot ng tuyn xung, a thng tin

nhn bit t bo, mng v tnh trng hin ti ca t bo (cu trc iu khin, cc lulng cn ri, ang s dng hoc nghn)

Knh nhn tin PCH: cung cp tin nhn tBS n MS, PCH pht IMSI ca thubao v yu cu pht li trn RACH- knh iu khin ngu nhin. Ngoi ra PCH cng

c thc dng cung cp cc bn tin qung b dng ASCII

Knh truy cp hng xung DACH chuyn bn tin tBS n MS trong 1 cell. Hai knh dnh ring:Knh iu khin dnh ring DCCH gm knh iu khin dnh ring ng mt

mnh SDCCH v knh iu khin lin kt ACCH.


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1.4.1.2 Knh lu lng

Dng truyn cc thng tin ca in thoi hoc s liu, bao gm 2 knh: Knh lu lng dng ring (DTCH) : chuyn d liu theo m hnh

kt ni im - im v2 hng n 1 thu bao v c s dng truyn thng

tin ngi dng.

Knh lu lng dng chung (CTCH): chuyn d liu theo mhnh kt ni im - im trn knh ng xung, s dng truyn thng tin

c nhn n tt c cc thu bao trong cng nhm.

1.4.2 Knh truyn ti

Knh truyn ti mang cc thng s, c tnh cn thit truyn ti cc thng tin

d liu qua mng.Cc knh truyn ti c hnh thnh nhvic sp xp cc knh logic.

C 2 loi knh truyn ti :

Knh truyn ti ring DCH: mang thng tin iu khin cho ring mt MSvi mang DCH-UL, DCH-DL.

Knh truyn ti chung CCH : dng chung cho tt c cc MSMi knh truyn ti cha mt m ch th nh dng truyn ti TFI (Transport

Format Indicator).TFI c s dng phi hp lm vic gia lp MAC v lp vt

l.Lp vt l s ghp a hp nhiu knh truyn ti vi nhau to thnh mt knh

truyn ti m ho hn hp CCTRCH (Transport Format Combination Indicator) v gi

km trong knh CCTRCH. T hp m TFCI c truyn i trong knh iu khin vt

l thng bo vi u thu knh truyn ti no ang c nhn. Tip , TFCI s

c gii m v to ra cc TFI tng ng gi ln lp trn.


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1.4.2.1 Knh truyn ti ring

Vi knh truyn ti ring ch c mt knh duy nht l knh DCH.Knh ny c thhot ng tuyn ln hoc tuyn xung.

1.4.2.2 Knh truyn ti chung

Knh truyn ti chung bao gm 6 knh: BCH, FACH, PCH, RACH, CPCH v

DSCH.

Knh BCH - knh qung b, l knh truyn ti ng xung, s dng qung b nhng thng tin trong h thng hay trong 1 t bo.

Knh FACH- Knh truy cp gi i, cng l knh truyn ti ng xung.C th hot ng trong ton b hay mt phn t bo. Vic gi knh ny c thc

hin sau khi BS nhn c bn tin truy nhp ngu nhin.

Knh PCHKnh tm gi, l knh mang d liu cn thit cho cc th tctin nhn, l khi h thng mun kt ni lien lc vi thu bao.

Knh RACH Knh truy cp ngu nhin, l knh mang thng tin iukhin tthu bao, nh yu cu thit lp mt kt ni.

Knh CPCH Knh d liu gi chung, l knh m rng ca knhRACH, c s dng truyn d liu user dng gi trn hng ln. i cp vi knh

ny, hng xung d liu gi c truyn trn knh FACH.

Knh DSCHKnh chia sng xung, l knh mang cc thng tin dliu hoc thng tin iu khin ca ngi dng.


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1.4.3 Knh vt l

Cc knh truyn ti c x l tip theo bng cch ghp vo cc knh vt l.Knh vt l c qun l v x l ti lp vt l.Vic x l y thc hin nhng k

thut bin i cn thit nhm tng thch c tnh truyn dn v tuyn v m bo cht

lng tn hiu cao nht.

1.4.3.1 Knh ng ln

Hai knh dnh ring:

DPDCH (truyn d liu) : DPCCH (truyn bo hiu) Mt knh truy cp chung RACH.Hu ht cc trng hp mi cuc gi chc cp mt knh DPDCH cho cc

dch v chia s thi gian.Cng c th cp nhiu knh, chng hn c h s tri ph

ln khi truyn d liu tc cao.

Hnh 1.10: Tc truyn WCDMA ng ln


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Knh DPDCH:Truyn pilot cho thu tng can.Truyn bit iu khin cng sut.Truyn tin tc v tc .

1.4.3.2 Knh ng xung

Knh vt l iu khin chung (s cp v th cp) CCPCH mang: BCCH,PCH, PACH.

Knh SCH cung cp nh thi v MS o lng SCH phc v chuyngiao.

Knh dnh ring (DPDCH v DPCCH) ghp knh theo thi gian. K hiupilot c ghp knh trn BCCH(theo thi gian) phc vthu tng quan. V cc k

hiu pilot l dnh ring cho mi kt ni nn n c dng nh gi s hot ng

thch ng ca anten, h triu khin cng sut nhanh hng xung. CCPCH scp

mang BCCH v knh pilot chung c ghp knh theo thi gian. CCPCH c m nh

nhau trong tt c cc cell.

Hnh 1.11: Cu trc knh dnh ring


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CCPCH th cp ghp knh theo thi gian PCH vi PACH trong cu trcsiu khung. Tc bn tin CCPCH l kh bin t cell ny sang cell khc.

Hnh 1.12: Cu trc knh CCPCH

Knh SCH- knh ng b, s dng cho th tc ng b mng. Dng khithc hin th tc nh vv ng b mng.

SCH s cp khng iu ch cung cp nh thi xc nh SCH th cp mSCH th cp c iu ch cung cp tin tc xc m PN ca BS. SCH s cp s dng m

256 bits khng iu ch, pht mi ln 1 khe. SCH th cp m 256 bits ciu ch,

pht song song vi SCH s cp. SCH th cp c iu ch vi chui nh phn 16 bits

(c lp cho mi khung). Chui iu ch ging nhau vi tt cBS c ttng quan

tt.

Knh PRACHKnh vt l truy xut ngu nhin, c s dng hngln mang thng tin truy xut mng. Trong mt vi trng hp dng pht thng tin sliu gi. Hnh 1.14 cho ta ci nhn s b v cht lng khe thi gian truy cp ca knh

RACH.


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Hnh 1.13: Cu trc knh ng b SCH

Hnh 1.14: Cht lng khe thi gian truy cp ca knh RACH


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1.5 Cu trc a l ca h thng thng tin di ng 3G

1.5.1 Phn chia theo vng mng

Trong mt quc gia c th c nhiu vng mng vin thng, vic gi vo mt

vng mng no phi c thc hin thng qua tng i cng. Cc vng mng di

ng 3G c i din bng tng i cng GMSC hoc GGSN. Tt c cc cuc gi

n mt mng di ng t mt mng khc u c nh tuyn n GMSC hoc GGSN.

Tng i ny lm vic nh mt tng i trung k vo cho mng 3G. y l ni thc

hin chc nng hi nh tuyn cuc gi kt cui trm di ng. GMSC/GGSN cho

php h thng nh tuyn cc cuc gi vo t mng ngoi n ni nhn cui cng: cc

trm di ng b gi.

1.5.2 Phn chia theo vng phc v MSC/VLR v SGSN

Mt mng thng tin di ng c phn chia thnh nhiu vng nhhn, mi vng

nhny c phc v bi mt MSC/VLR (hnh 1.15a). hay SGSN (1.15b). Ta gi y

l vng phc v ca MSC/VLR hay SGSN.

Hnh 1.15: Phn chia mng thnh cc vng phc v ca MSC/VLR v SGSN


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nh tuyn mt cuc gi n mt thu bao di ng, ng truyn qua mng s

c ni n MSC ang phc v thu bao di ng cn gi. mi vng phc v

MSC/VLR thng tin vthu bao c ghi li tm thi VLR. Thng tin ny bao gmhai loi:

Thng tin vng k v cc dch v ca thu bao. Thng tin v v tr ca thu bao ( thu bao ang vng nh v hoc vng

nh tuyn no ).

1.5.3 Phn chia theo vng nh vv vng nh tuyn

Mi vng phc v MSC/VLR c chia thnh mt s vng nh v: LA

(Location Area) hnh 1.16a. Mi vng phc v ca SGSN c chia thnh cc vng

nh tuyn RA ( Routing Area ) hnh 1.16b.

Hnh 1.16: Phn chia vng phc v ca MSC/VLR v SGSN thnh cc vng

nh v(LA: Location Area) v nh tuyn (RA: Routing Area)


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Vng nh v (hay vng nh tuyn l mt phn ca vng phc v MSC/VLR

(hay SGSN) m mt trm di ng c th chuyn ng t do v khng cn cp

nht thng tin v v tr cho MSC/VLR (hay SGSN) qun l v tr ny. C th ni vngnh v(hay vng nh tuyn) l v tr c th nht ca trm di ng m mng cn bit

nh tuyn cho mt cuc gi n n. vng nh v ny thng bo tm sc pht

qung b tm thu bao di ng b gi. H thng c th nhn dng vng nh v bng

cch s dng nhn dng vng nh v (LAI: Location Area Identity) hay nhn dng

vng nh tuyn (RAI Routing Area Identity). Vng nh v(hay vng nh tuyn) c

th bao gm mt s v thuc mt hay nhiu RNC, nhng ch thuc mt MSC (hay

mt SGSN).

1.5.4 Phn chia theo

Vng nh vhay vng nh tuyn c chia thnh mt s hnh 1.17.

Hnh 1.17: Phn chia LA v RA

l mt vng ph v tuyn c mng nhn dng bng nhn dng ton cu

CGI (Cell Global Identity ). Trm di ng nhn dng bng m nhn dng trm gc


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BSIC (Base Station Identity Code). Vng ph ca cc thng c m phng bng

hnh lc gic tin cho vic tnh ton thit k.

1.5.5 Mu

Mu c hai kiu: v hng ngang (omnidirectional) v phn on (sectorized).

Cc mu ny c cho trn hnh 1.18.

Hnh 1.18: Cc kiu mu

v hng ngang (hnh 1.18a) nhn c t pht x ca mt anten c bp sngtrn trong mt ngang (mt phng song song vi mt t) v bp sng c hng chc

xung mt t trong mt ng (mt phng vung gc vi mt t). phn on (hnh

1.18b) l nhn c t pht x ca ba anten vi hng pht x cc i lch nhau

1200. Cc anten ny c bp sng dng na s 8 trong mt ngang v trong mt ng bp

sng ca chng chc xung mt t. Trong mt strng hp phn on c thc

to ra t pht x ca nhiu hn ba anten. Trong thc t mu c th rt a dng ty

vo a hnh cn ph sng. Tuy nhin cc mu nh trn hnh 1.16 thng c sdng thit kcho s ph sng chun.


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1.6 Kt lun chng

Chng ny trc ht xt tng quan qu trnh pht trin thng tin di ng ln 4G.Nu cng ngha truy nhp cho 3G l CDMA bng rng th cng ngha truy nhp

cho 4G l OFDMA. Sau kin trc mng 3G c xt. Cc pht hnh nh du cc

mc quan trng pht trin mng 3G WCDMA UMTS c xt: R3, R4, R5 v R6. R3

bao gm hai min chuyn mch knh v chuyn mch gi trong kt ni gia cc nt

chuyn mch gi l TDM (ghp knh theo thi gian). R4 l s pht trin ca R3 trong

min chuyn mch knh chuyn thnh chuyn mch mm v kt ni gia cc nt

mng bng IP. R5 v R6 h tr cc dch v a phng tin IP hon ton da trn

chuyn mch gi. p ng c nhim v ny ngoi min chuyn mch gi, mng

c b sung thm phn ha phng tin IP (IMS). Ct li ca IMS l CSCF thc

hin khi u kt ni a phng tin IP da trn giao thc khi u phin (SIP Session

Initiation Protocol). Ngoi ra IMS vn cn cha chuyn mch mm h trdch v

chuyn mch knh (MGCF). Hin nay mng 3GWCDMA UMTS ang giai don

chuyn dn t R4 sang R5. Cui chng trnh by cu trc a l ca mt mng thng

tin di ng 3G c cha c vng chuyn mch knh v vng chuyn mch gi.


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CHNG II: CC CNG NGH TRUY NHP CA

H THNG THNG TIN DI NG WCDMA/UMTS

Chng 2 gii thiu v cc cng ngh truy nhp WCDMA trong h thng UMTS,

t gip chng ta c ci nhn tng quan v h thng WCDMA/UMTS, l nhng

u im v nhc im ca h thng. Gip ta khai thc mt cch hiu qu khi s dng

h thng thng tin di ng WCDMA/UMTS.

2.1 Cng ngh WCDMA2.1.1 Gii thiu cng ngh WCDMA

WCDMA (Wideband CDMA) l cng nghthng tin di ng th h3 gip tng

tc truyn nhn d liu cho h thng GSM bng cch dng k thut CDMA hot

ng bng tn rng thay th cho TDMA. Trong cc cng nghthng tin di ng th

h 3 th WCDMA nhn c sng h ln nht nhvo tnh linh hot ca lp vt l

trong vic h tr cc kiu dch v khc nhau, c bit l dch v tc bit thp vtrung bnh.

2.1.2 u im v nhc im ca h thng WCDMA

a. u im

L h thng truy cp phn chia theo m tri ph trc tip, c tc bit cao (lnn 2Mbps).

Tc chip 3,84 Mcps vi rng sng mang 5MHZ, do h trtc dliu cao em li nhiu li ch nh li a phn tp.


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H trtc ngi s dng thay i lin tc, Mi ngi s dng cung cp mtkhung, trong khung tc d liu gi c nh nhng tc c th thay i t

khung ny n khung khc.H trhai m hnh v tuyn FDD v TDD. Trong m hnh FDD sng mang

5MHZ s dng cho ng ln v ng xung, cn trong m hnh TDD sng mang

5MHZ chia s theo thi gian gia ng ln v ng xung.

WCDMA h trhot ng khng ng b ca cc trm gc, do d dng phttrin cc trm gc va v nh.

WCDMA s dng tch sng tham chiu n sng mang da trn knh hoa tiu,do c thnng cao dung lng v vng ph.

WCDMA c thit k d dng nng cp hn cc h thng CDMA nh tchsng a ngi s dng, s dng angten thng minh nng cao dung lng v vng

ph.

WCDMA c thit k tng thch vi GSM m rng vng ph sng vdung lng ca mng.

Lp vt l mm do d thch hp c tt c thng tin trn mt sng mang.H s ti s dng tn s bng 1.H trphn tp pht v cc cu trc thu tin tin.b. Nhc im

Nhc im chnh ca WCDMA l h thng khng cho php trong bng TDD

pht lin tc cng nh khng to iu kin cho cc k thut chng nhiu cc mi

trng lm vic khc nhau.

H thng thng tin di ng th h 3 WCDMA c th cung cp cc dch v vi tcbit ln n 2Mbps. Bao gm nhiu kiu truyn dn nh truyn dn i xng v

khng i xng, thng tin im n im v thng tin a im. Vi khnng , cc

h thng thng tin di ng th h 3 c th cung cp d dng cc dch v mi nh: in


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thoi thy hnh, ti d liu nhanh, ngoi ra n cn cung cp cc dch va phng tin

khc.

2.2 Tri ph sdng trong h thng WCDMA

2.2.1 c im ca tri ph

Trong cc h thng thng tin thng thng rng bng tn l vn quan tm

chnh v cc h thng ny c thit k s dng cng t rng bng tn cng tt.

Trong cc h thng iu chbin song bin, rngbng tn cn thit pht mt

ngun tn hiu tng t gp hai ln rng bng tn ca ngun ny. Trong cc h

thng iu tn rng bng tn ny c th bng vi ln rng bng tn ngun ph

thuc vo ch siu ch. i vi mt tn hiu s, rng bng tn cn thit c cng

gi tr vi tc bit ca ngun. rng bng tn chnh xc cn thit trong trng hp

ny ph thuc v kiu iu ch (BPSK, QPSK v.v...).

Trong cc h thng thng tin tri ph (vit tt l SS: Spread Spectrum) rng

bng tn ca tn hiu c mrng, thng thng hng trm ln trc khi c pht.

Khi ch c mt ngi s dng trong bng tn SS, s dng bng tn nh vy khng c

hiu qu. Tuy nhin mi trng nhiu ngi s dng, cc ngi s dng ny c th

dng chung mt bng tn SS (tri ph) v h thng trnn s dng bng tn c hiu

sut m vn duy tr c cc u im ca tri ph.

Mt h thng thng tin sc coi l SS (tri ph) nu:

- Tn hiu c pht chim rng bng tn ln hn rng bng tn ti thiu

cn thit pht thng tin.

- Tri phc thc hin bng mt m c lp vi sliu.

C ba kiu h thng SS c bn: chui trc tip (DSSS: Direct-Sequence

Spreading Spectrum), nhy tn (FHSS: Frequency-Hopping Spreading Spectrum) v


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nhy thi gian (THSS: Time-Hopping Spreading Spectrum). Cng c th nhn c

cc h thng lai ghp t cc h thng ni trn. WCDMA s dng DSSS.

2.2.2 Tri ph chui trc tip (DSSS)

DSSS t c tri ph bng cch nhn lung s cn truyn vi mt m tri ph

c tc chip (Rc=1/Tc, Tc l thi gian mt chip) cao hn nhiu tc bit (Rb=1/Tb, Tb

l thi gian mt bit) ca lung s cn pht. Hnh 2.1 minh ha qu trnh tri ph trong

Tb=15Tc hay Rc=15Rb. Hnh 2.1a cho thy s n gin ca b tri ph DSSS

trong lung s cn truyn x c tc Rbc nhn vi mt m tri ph c tc Rcc lung u ra y c tc Rc ln hn nhiu so vi tc Rb ca lung vo. Cc

hnh 2.1b v 2.1b biu th qu trnh tri ph trong min thi gian v min tn s.

Ti pha thu lung y c thc hin gii tri ph khi phc li lung x bng

cch nhn lung ny vi m tri ph c ging nh pha pht: x=yc.

Hnh 2.1: Tri ph chui trc tip (DSSS)


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x, y v c k hiu tng qut cho tn hiu vo, ra v m tri ph; x(t), y(t) v c(t) k

hiu cho cc tn hiu vo, ra v m tri ph trong min thi gian; X(f), Y(f) v C(f) khiu cho cc tn hiu vo, ra v m tri ph trong min tn s; Tb l thi gian mt bit

ca lung s cn pht, Rb=1/Tb l tc bit ca lung s cn truyn; Tc l thi gian

mt chip ca m tri ph, Rc=1/Tc l tc chip ca m tri ph. Rc=15Rb v Tb=15Tc.

2.2.3 p dng DSSS vo WCDMA

Trong cng ngha truy nhp phn chia theo m da trn CDMA, mt tp m

trc giao c s dng v mi ngi s dng c gn mt m tri ph ring. Cc m

tri ph ny phi m bo iu kin trc giao sau y:

Tch hai m ging nhau bng 1: cici=1Tch hai m khc nhau s l mt m mi trong tp m: cicj=ckC s bit 1 bng s bit -1 trong mt m

1

10

N

kk

CN

, trong N l s chip v

Ck l gi tr chip k trong mt m.

Bng 2.1. Th d b tm m trc giao

c0 +1 +1 +1 +1 +1 +1 +1 +1

c1 +1 +1 +1 +1 -1 -1 -1 -1

c2 +1 +1 -1 -1 +1 +1 -1 -1c3 +1 +1 -1 -1 -1 -1 +1 +1

c4 +1 -1 +1 -1 +1 -1 +1 -1

c5 +1 -1 +1 -1 -1 +1 -1 +1


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c6 +1 -1 -1 +1 +1 -1 -1 +1

c7 +1 -1 -1 +1 -1 +1 +1 -1

Bng 2.2. Th d nhn hai m ging nhau trong bng 1 c mt

c1 +1 +1 +1 +1 -1 -1 -1 -1

c1 +1 +1 +1 +1 -1 -1 -1 -1

c1 c1 +1 +1 +1 +1 +1 +1 +1 +1

Bng 2.3. Th d nhn hai m khc nhau trong bng 1 c mt m mi

trong tp 8 m

c1 +1 +1 +1 +1 -1 -1 -1 -1

c3 +1 +1 -1 -1 -1 -1 +1 +1=

c2

+1 +1 -1 -1 +1 +1 -1 -1

Nu ta xt mt h thng gm K ngi s dng c xy dng trn c sCDMA,

th sau tri phcc ngi s dng ny s pht vo khng gian tp cc tn hiu y nh

sau:

1 1

K K

i i ii i

y y c x

(2.1)

Ta xt qu trnh x l tn hiu ny ti mt my thu k. Nhim v ca my thu ny

l phi ly ra xk v loi b cc tn hiu khc (cc tn hiu ny c gi l nhiu ng


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knh v trong h thng CDMA chng c pht trn cng mt tn s vi xk). Nhn

(2.1) vi xk v p dng quy tc trc giao ni trn ta c:

1

K

k k i i ii k

x x c x

(2.2)

Thnh phn th nht trong (2.2) chnh l tn hiu hu ch cn thnh phn th hai

l nhiu ca cc ngi s dng cn l nhiu ca cc ngi s dng khc c gi l

MAI (Multiple Access Interferrence: nhiu a ngi s dng). loi b thnh phn

th hai my thu s dng b lc tng quan trng min thi gian kt hp vi b lc tn

s trong min tn s. Hnh 2.2 xt qu trnh gii tri ph v lc ra tn hiu hu ch ti

my thu k trong mt h thng CDMA c K ngi s dng vi gi thit cng sut pht

t K my pht nh nhau ti u vo my thu k. Hnh 2.2a cho thy s gii tri ph

DSSS. Hnh 2.2b cho thy ph ca tn hiu tng c pht i t K my pht sau tri

ph, hnh 2.2c cho thy ph ca tn hiu ny sau gii tri ph ti my thu k v hnh

2.2d cho thy ph ca tn hiu sau b lc thng thp vi bng thng bng Rb.

Hnh 2.2. Qu trnh gii tri ph v lc tn hiu ca ngi sdng k tK tn hiu


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T hnh 2.2 ta thy t s tn hiu trn nhiu (SIR: Signal to Interference Ratio) l

t s gia din tch hnh ch nht c t m trn hnh 2.2.b v tng din tch cc

hnh ch nht trng trn hnh 2.2.c: SIR=S1/S2. T s ny t l vi t s Rc/Rb. v th ts Rc/Rb c gi l li x l (TA: Processing Gain).

2.3 Chuyn giao trong h thng WCDMA/UMTS

2.3.1 Tng quan v chuyn giao trong mng di ng

Chuyn giao l mt khi nim cbn ca s di chuyn trong cu trc cell. Trong

h thng UMTS c nhiu loi chuyn giao khc nhau ph hp vi cc yu cu khcnh: iu khin ti, cung cp vng ph sng v tho mn cht lng dch v .

Mc tiu ca chuyn giao l cung cp s lin tc ca dch v di ng khi ngi

s dng di chuyn qua vng bin ca cc cell trong kin trc cell. ngi s dng c

th tip tc thng tin v bng qua bin ca cell th cn cung cp ti nguyn v tuyn

mi cho ngi s dng cell mi, hay cn gi l cell ch. Bi v cng tn hiu

thu c xu hn cell ch m ngi s dng chuyn qua. Qu trnh x l ng

xung cn tn ti kt ni trong cell hin ti v thit lp kt ni mi trong cell ln cn

gi l chuyn giao. Tnh nng ca mng t bo th hin qua chuyn giao l ch yu

nhm cung cp dch v hp dn nhcc ng dng thi gian thc hay lung a phng

tin nhcc d n trong mng di ng th h 3 ba a ra. S lng chuyn giao khng

thnh cng th hin th tc chuyn giao khng hon thnh.

2.3.2 Cc loi chuyn giao trong h thng WCDMA/UMTS

Chuyn giao trong mng WCDMA c thc phn loi theo nhiu cch khc

nhau. C th phn thnh: chuyn giao cng tn s, chuyn giao khc tn s v chuyn

giao gia cc mng khc nhau WCDMS vi GSM. Trong phn ny, ta li chia chuyn


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giao trong WCDMA thnh bn loi: chuyn giao trong cng h thng, chuyn giao

ngoi h thng, chuyn giao cng, chuyn giao mm v mm hn.

Hnh 2.3: Cc loi chuyn giao trong h thng 3G

Chuyn giao trong cng h thngChuyn giao trong cng h thng c thc chia thnh chuyn giao cng tn s

v chuyn giao khc tn s. Chuyn giao cng tn s xut hin gia cc cell cng sng

mang WCDMA. Chuyn giao khc tn s xut hin gia cc cell hot ng trn cc tn

s sng mang khc nhau.

Chuyn giao ngoi h thngChuyn giao ngoi h thng xut hin gia cc cell thuc hai k thut truy nhp

v tuyn khc nhau RAT (RAT: Radio Access Technology) hoc gia hai node

UTRAN FDD v UTRAN TDD.

Chuyn giao cng l loi chuyn giao m kt ni c b ph vtrc khi c ktni v tuyn mi c thit lp gia thit b ngi s dng v mng truy nhp v

tuyn. Loi chuyn giao ny s dng trong mng GSM gn cc knh tn s khc

nhau cho cc cell. Ngi s dng i vo cell mi s hu b kt ni c v thit lp kt

ni mi vi tn s mi.


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Chuyn giao cng trong mng UMTS s dng thay i knh tn s ca UE v

UTRAN. Trong sut qu trnh b tr tn s ca UTRAN, n s xc nh rng mi hot

ng UTRAN l d dng yu cu thm vo ph tn t c dung lng khi cccp s dng hin ti ht. Trong trng hp ny vi bng tn xp x 5 MHz c

s dng bi mt ngi v cn chuyn giao gia chng.

Chuyn giao cng cn p dng thay i cell trn cng tn s khi mng khng

h tr tnh a dng ln. Trong trng hp khc l khi knh truyn c xc nh

trong khi ngi s dng i vo cell mi th chuyn giao cng s thc hin nu chuyn

giao mm v mm hn khng thc hin c .

Thng thng chuyn giao cng ch dng cho vng ph v ti, cn chuyn giao

mm v mm hn l yu t chnh h trdi ng. Chuyn giao gia hai mode UTRAN

FDD v UTRAN TDD cng thuc loi chuyn giao cng.

Chuyn giao mm v mm hn

Hnh 2.4: Chuyn giao mm v mm hn

Chuyn giao mm l chuyn giao gia hai BS khc nhau, cn chuyn giao mm

hn l chuyn giao gia t nht 2 sector ca cng mt BS. Trong sut qu trnh chuyn

giao mm, MS giao tip mt cch tc th vi hai (chuyn giao hai ng) hoc nhiu


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cell ca cc BS khc nhau thuc cng RNC (Intra-RNC) hoc cc RNC khc nhau

(Inter-RNC). Trn ng xung my di ng nhn hai tn hiu vi t s kt hp ln

nht; ng xung, my di ng m ho knh c tch bi cng hai BS (chuyngiao hai ng), v c gi n RNC cho vic la chn kt hp. Hai hot ng iu

khin cng sut vng c bit trong chuyn giao mm cho mt BS. Trong trng hp

chuyn giao mm hn, MS c iu khin t nht bi hai sector ca cng BS, do

ch c mt hot ng iu khin cng sut vng. Chuyn giao mm v mm hn ch s

dng mt sng mang, do y l chuyn giao trong cng h thng. Hnh (2.5) th

hin cc loi chuyn giao khc nhau.

chuyn giao hai ng l chuyn giao m MS thng tin vi hai onca hai khc nhau

chuyn giao ba ng l chuyn giao m MS thng tin vi ba onca hai khc nhau

BS iu khin trc tip qu trnh x l cuc gi trong qu trnh chuyn giao mm

c gi l BS scp. BS scp c th khi u bn tin iu khin ng xung, cc

BS khc khng x l cuc gi gi l BS th cp.Chuyn giao mm kt thc khi hoc

BS scp hoc BS th cp b loi b.

Hnh 2.5: Cc loi chuyn giao khc nhau trong mng WCDMA

Chuyn giao hai ng

O A O B

O AO B

O C

Chuyn giao ba ng


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2.4 iu khin cng sut

Trong trng hp mt my pht gy nhiu n gn my thu k (n gn nt Bchng hn), cng sut ca my pht ny tng cao dn n MAI tng cao, t s tn hiu

trn nhiu gim mnh v my thu k khng th tch ra c tn hiu ca mnh. Hin

tng ny c gi l hin tng gn v xa. trnh hin tng ny h thng phi

iu khin cng sut sao cho cng sut thu ti nt B ca tt ccc UE u bng nhau

(l tng). iu khin cng sut trong WCDMA c chia thnh:

iu khin cng sut vng h iu khin cng sut vng kniu khin cng sut vng hc thc hin tng ti UE khi n thc hin th

tc xin truy nhp Nt B (da trn cng sut m n thu c tknh hoa tiu pht i t

B), khi ny UE cha c kt ni vi nt ny. Cn iu khin cng sut vng kn c

thc hin khi UE kt ni vi nt B. iu khin cng sut vng kn li c chia

thnh:

iu khin cng sut vng trong c thc hin ti nt B. iu khincng sut vng trong c thc hin nhanh vi 1500 ln trong mt giy da trn so

snh SIR thu vi SIR ch

iu khin cng sut vng ngoi c thc hin ti RNC thit lp SIRch cho nt B. iu khin cng sut ny da trn so snh t l li khi (BLER) thu

c vi t lch.

2.5 My phn tp pht hay my thu RAKE

Phainh a ng trn knh v tuyn dn n tn thi v chn lc tn s lm

hng tn hiu thu. nh gi hin tng tn thi trn ng truyn v tuyn, ngi ta

pht i mt xung hp (xung kim) v o p ng xung ny ti pha thu. p ng ny l


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bc tranh th hin s ph thuc cng sut ca cc ng truyn khc nhau n my thu

vo thi gian tr ca cc ng truyn ny. p ng ny c gi l l lch tr cng

sut. Hnh 2.6a cho thy truyn sng a ng v hnh 2.6b cho thy th d v l lchtr cng sut.

Hnh 2.6: Truyn sng a ng v l lch tr cng sut


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Hnh 2.7: My thu RAKE

Chui tn hiu gi ngu nhin c pht i CDMA c thuc tnh l cc phin

bn dch thi ca n ti pha thu hu nh khng tng quan. Nh vy mt tn hiu

c truyn tmy pht n my thu theo nhiu ng khc nhau (thi gian tr khc

nhau) c thc phn gii vo cc tn hiu phainh khc nhau bng cch ly tng

quan tn hiu thu cha nhiu phin bn dch thi ca chui gi ngu nhin. My thu s

dng nguyn l ny c gi l my thu phn tp a ng hay my thu RAKE (hnh

2.7).Trong my thu RAKE nhn c cc phin bn dch thi ca chui ngu

nhin, tn hiu thu phi i qua ng tr trc khi c ly tng quan v c kt

hp. ng tr bao gm nhiu mt tr c thi gian tr bng thi gian mt chip Tc. My


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thu dch nh thi bn sao m tri ph tng chip cho tng k hiu thng tin gii tri

ph k hiu trong vng mt k hiu v to nn l lch tr cng sut (xem hnh 2.7a).

Vi tham kho l lch tr cng sut (bc tranh th hin cng sut v tr ca cc ngtruyn) c to ra, my thu chn cc ng truyn c cng sut vt ngng kt

hp RAKE trn c sslng btng quan, bc tnh knh v b b trthay i

pha (c gi l cc ngn my thu RAKE). Trong trng hp p dng thu phn tp

khng gian hay phn tp gia cc on , l lch tr cng sut c to ra cho mi

nhnh v cc ng truyn c chn t l lch tr cng sut sut tng hp ca tt c

cc nhnh. Trong thc t, v cc tn hiu tri ph gm nhiu ca cc ngi s dng

khc v cc tn hiu a ng ca knh ngi s dng, nn gi trngng c lp

d trn mc cng sut tp m nn v cc ng truyn c SIR hiu dng (c cng

sut thu vt ngng) c chn. V MS chuyn ng (hoc mi trng truyn sng

thay i khi MS cnh), nn vtr ng truyn (thi gian tr) c kt hp RAKE

cng sthng xuyn thay i, my phi nh k cp nht l lch trng truyn v

cp nht cc ng truyn c kt hp RAKE trn c s l lch mi (qu trnh ny

c gi l tm kim ng truyn v n lin quan n tm kim ng truyn kt

hp RAKE).


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2.6 Kt lun chng

H thng thng tin di ng th h 3 cn gi l IMT- 2000 c cc t chcquc ta ra cc tiu chun v k thut nhm p ng kp thi cho vic trin khai h

thng vo thc t. Trong UMTS l mt h thng thng tin di ng c nhiu u im

ni tri hn cc h thng 2G. Tuy nhin n pht trin da trn cc th h trc.

Chng ny trnh by cc vn c bn v cu trc mng truy nhp v tuyn

UMTS, slc v nhng dch v v ng dng ca n trong h thng thng tin di ng

th h ba. Trong chng 3, ta s tip tc tm hiu v cc k thut iu khin cng sut

trong h thng thng tin di ng th h ba.


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CHNG III: IU KHIN CNG SUT TRONG

H THNG WCDMA/UMTS

Trc khi i tm hiu viu khin cng sut trong h thng thng tin di ng

WCDMA/UMTS, chng ta phi c ci nhn khi qut viu khin cng sut trong

cc h thng trc 3G, chnh l iu khin cng sut trong GSM, iu khin cng

sut trong CDMA-IS95A. WCDMA/UMTS chnh l chin lc pht trin i ln t h

thng thng tin di ng GSM, s dng cng ngh CDMA bng rng (nn tng l

CDMA bng hp, trong h thng thng tin di ng CDMA IS-95A). T gip chng

ta c ci nhn su sc v ton din v h thng thng tin di ng WCDMA/UMTS.

3.1 Khi nim viu khin cng sut

Tn hiu tcc MS khc nhau c truyn i trong cng bng tn mt cch ng

thi trong cc h thng WCDMA. Khi cha c iu khin cng sut tn hiu t MS gn

vi BS nht c th chn cc tn hiu tcc MS khc cch BS hn. Trong tnh hungxu nht, mt MS c cng sut qu ln c th chn ton b mt cell. Vy cch gii

quyt ti u nht l ta phi iu khin cng sut. Vy iu khin cng sut l g?Ti

sao n li gii quyt c vn ?

Hnh 3.1: Hiu ng gn xa (iu khin cng sut ng ln)


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iu khin cng sut chnh l l vic ta m bo rng cc tn hiu n tu

cui khc nhau c cng cng sut hay c cng t s tn hiu trn nhiu (SIR) khi

chng n BS.

3.2 Mc ch v ngha ca vic iu khin cng sut

3.2.1 Mc ch ca iu khin cng sut

Nh ta bit cng ngh WCDMA l mt trong nhng cng ngh truy nhp v

tuyn ph bin c s dng trong h thng thng tin di ng th h th 3 UMTS. Vi

c im a ngi s dng chung mt tn s song mang, nh hng ca loi nhiu nh

: hiu ng gn xa, nhiu ng knh, nhiu gia cc ln cnl khng th trnh khi,

iu khin cng sut s chu trch nhim iu chnh cng sut ng ln v ng

xung gim thiu mc nhiu ny nhm m bo QoS yu cu.

Muc ch ca iu khin cng sut l gii hn cng sut pht trn ng ln v

ng xung trong khi vn duy tr cht lng ca ng truyn mi iu kin.

3.2.2 ngha vic iu khin cng sut

minh ho vic iu khin cng sut cn thit nh th no trong h thng

WCDMA, chng ta xem xt mt n l c hai thu bao ginh. Thu bao 1 gn

trm gc hn thu bao 2. Nu khng c iu khin cng sut, c hai thu bao s pht

mt mc cng sut cnh p, tuy nhin do s khc nhau v khong cch nn cng sut

thu t thu bao 1 l pr1 s ln hn thu bao 2 l pr2. Gi s rng v lch v khong

cch nh vy m pr1 ln gp 10 ln pr2 th thu bao 2 s chu mt s bt li ln.

Nu t s SNR yu cu l (1/10) th chng ta c th nhn ra s chnh lch gia

cc SNR ca hai thu bao. Hnh (3.2) minh hoiu ny. Nu chng ta b qua tp m

nhit th SNR ca thu bao 1 s l 10 v SNR ca thu bao 2 s l (1/10). Thu bao 1


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c mt SNR cao hn nhiu v nh vy n sc c mt cht lng rt tt, nhng

SNR ca thu bao 2 ch va so vi yu cu. S khng cn bng ny c xem l bi

ton xa-gn kinh in trong mt h thng a truy cp tri ph.H thng ni trn c coi nh t ti dung lng ca n. L do l nu chng

ta tha thm mt thu bao th 3 pht cng mc cng sut p vo bt c ch no

trong th SNR ca thu bao th3 s khng tht c gi tr yu cu. Hn na,

nu chng ta ca thm thu bao th 3 vo h thng th thu bao th3 s khng

nhng khng t c SNR yu cu m cn lm cho SNR ca thu bao 2 b gim

xung di mc SNR yu cu

Hnh 3.2: Cng sut thu thai thu bao trm gc

Vic iu khin cng sut c a vo gii quyt vn xagn v tng

ti a dung lng h thng. iu khin cng sut l iu khin cng sut pht t mi

thu bao sao cho cng sut thu ca mi thu bao trm gc l bng nhau. Trong mt ,

nu cng sut pht ca mi thu bao c iu khin cng sut thu ca mi thu

bao trm gc l bng vi Pr th nhiu thu bao hn c th s dng trong h thng. V

P

f

Thu bao 1 cS/N = 1

Thu bao 2 cS/N = 1/10


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d trn, nu SNR yu cu vn l (1/10) th tng cng c thc 11 thu bao c s

dng trong (hnh 3.2). Dung lng c tng ti a khi s dng iu khin cng sut.

iu khin cng sut nhm mc ch chng li hiu ng Fading Rayleigh trn tnhiu truyn i bi vic b cho Fading nhanh ca knh truyn.

Ngoi ra vic iu khin cng sut cn c tc dng gim nhiu a ng. V

cng sut pht ca my di ng thp nn lm tng tui th ca pin.

3.3 Skhc bit gia iu khin cng sut trong GSM, CDMA-IS95, v h thng

WCDMA/UMTS

Vi cng ngh GSM ch c MS mi phi thay i cng sut do lc gn lc

xa trm BS. Vic iu khin cng sut ny mt phn l tit kim nng lng mt

phn l cn bng cng sut pha thu. Bs khng c iu khin cng sut hay ni

ng hn l chiu chnh mt ln khi ci t h thng vic ny c gii thch l do

mt BS s qun l mt a bn cnh ,do vy phi c cng sut pht cnh

iu khin cng sut thc hin mt cch c lp gia hng ln v hng xung

gia cc MS do BSS iu khin, phm vi iu khin ni chung l 30dB vi tng nc

bin i l 2dB. Cn c vo s liu o ca BTS v mc cng sut cc i tn hiu thu

c t MS v cht lng ca tn hiu , BSS tnh ra cng sut truyn dn cn thit

ca MS v pht lnh n MS. ng thi BSS cng tnh ra cng sut truyn dn cn

thit ca BTS cho mi cuc ni.

Bt u cho mi cuc lin lc ,BSC quy dnh mc cng sut pht bn tin u tin

ca MS l nh nhau i vi mi MS .V sau iu chnh cng sut vi tc 2 dB

cho mi bc 60ms.

Trong GSM, cng sut pht thng c iu chnh trc mt mc no

chkhng iu chnh nh CDMA.

GSM ch c 2 loi KCS vng hv vng kn


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Chu kiu khin cng sut : 16Hz

Bc iu khin cng sut : 2dB

iu khin cng sut trong CDMA : trong h thng FDMA v TDMA iu

khin cng sut khng nh hng n dung lng nhng trong h thng CDMA th

iu khin cng sut l bt buc v phi nhanh nu khng dung lng h thng s

gim.Dung lng ca h thng CDMA t gi tr cc i nu cng sut pht ca cc

my di ng c iu khin sao cho cng sut thu c trm gc l nh nhau i

vtt cngi s dng.

iu khin cng sut c s dng cho ng ln trnh hin tng gn xa v

gim thiu nh hng ca nhiu h thng. i vi ng xung khng cn iu khin

cng sut h thng n v nhiu gy ra bi ngi s dng khc lun mc khng

i i vi tn hiu hu ch.Tt c cc tn hiu pht t trm gc ti my di ng u

c pht chung cng lc v th khng xy ra s khc bit tn hao truyn sng nh

ng ln.

Ngoi vic gim hin tng gn xa iu khin cng sut cn c s dng

trnh hin tng che ti v duy tr cng sut pht trn mt ngi s dng m bo t

s li bt mc cho trc ti thiu chp nhn c.

Trong h thng CDMA s dng hai phng php iu khin cng sut l iu

khin cng sut vng h(OPC) v iu khin cng sut vng kn (CPC) kt hp nhau.

Cn trong h thng WCDMA phng php iu khin cng sut vng h ch c

dung thit lp cng sut gn ng khi truy cp mng ln u tin

Ngoi tit kim cng sut pht ca BTS v MS,khc vi GSM, iu khin cng

sut trong CDMA cn phi iu khin cng sut pht ca cc MS sao cho cc tn hiu

uplink n BTS c mc cng sut bng nhau gim nh hng ln nhau gia cc

knh Uplink (hiu ng gn xa).


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Trong CDMA BTS lin tc gim dn cng sut pht v khi FER bt u tng

(tn hiu hi tip t MS)th BTS stng cng sut pht.

Chu kiu khin cng sut : 800HzBc iu khin cng sut : 1dB

WCDMA

Chu kiu khin cng sut :khe thi gian = 1500 Hz

Bc iu khin cng sut : 0,5 1 1,5 v 2 dB

tm hiu khn viu khin cng sut trong tng h thng, chng ta si

su phn tch tng h thng thy c s cn thit ca vic iu khin cng sut

trong cc h thng thng tin di ng.

3.4 iu khin cng sut trong GSM

3.4.1 ngha iu khin cng sut trong GSM

o Gim nhiu:- Tng s MS c mc C/I tt nht. Li ch thu c l gim thiu mc nhiu

nn ton mng (I).

o Gim cng sut tiu th:- Khi iu khin cng sut BTS c s dng trn tt c cc BTS trong mng,

tng s cng sut pht s gim khi so snh vi khng c iu khin cng sut. iu

ny cho thy nhiu ng knh v nhiu cn knh ng downlink trong mng gim.

- Trong trng hp b mt in ngun, trm pht s phi s dng ngun cquyd phng. Khi iu khin cng sut BTS c s dng th cng sut tiu th cquy s

gim v thi gian thoi s c th tng ln ti a.

o Tng kh nng s dng li tn s trong mng (kt hp cng vi nhytn vpht khng lin tc DTX).


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3.4.2 Phn loi iu khin cng sut trong GSM v c im iu khin cng sut

trong GSM

a. phn loi iu khin cng sut

C 2 cch iu khin cng sut: iu khin cng sut ng ln ti MS v iu

khin cng sut ng xung ti BTS

iu khin cng sut ng ln ti MS: MS t o cng sut thu c t BTS ri

c lng khong cch t n n BTS, sau t nh ra mc cng sut pht i.

iu khin cng sut ng xung ti BTS: s do BSC m nhn, tnh ton thm

cc thng s truyn sng, sau nh ra mc cng sut pht cn thit cho MS.

Cc mc cng sut c nh c a ra trong bng di.

b. c im iu khin cng sut trong GSM

-cc trm MS s dng ch mc cng sut cn ti thiu m bo vic lin lctin cy vi BTS.

-Trong GSM thit lp 8 bc BTS v 5 bc MS theo cng sut b pht nu trongbng di.

-Cng sut bpht BTS c iu chnh ri rc vi mi nc bng 2 dB. Viciu chnh cng sut b pht gim nhiu ng knh v do vy dn n tng yu t s

dng lp li tn sv tng dung lng h thng.

-Cng sut b pht BTS c th gim n gi tr ti thiu bng =13 dBm ( P1 = 20mW).

-iu khin cng sut trong MS s dng h thng iu khin cng sut vnght BTS.

-Di cng sut ra MS chia thnh 15 mc vi mi nc 2 dB ( t 2 - 30dB). Sthay i bt k1 nc l 2 DB trong khang thi gian ca mi khe ( c ngha l trong

khang 0.577ms).


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Di ng tn hiu nhn c BTS t 116 dB, do vy vn khong cch gn

xa c th gii quyt bng thc nghim.

Bng 3.1: Bc cng sut ti MS v BTS

Bc cng sut BTS, W MS, W

1 320 20

2 160 8

3 80 5

4 40 2

5 20 0.8

6 10 -

7 5 -

8 2.5 -

3.4.3 iu khin cng sut ng ln (t MS n BTS)

iu khin cng sut ng ln thng c s dng khi MS truy nhp mng ln

u, trong qu trnh thit lp ng truyn v tuyn s dng c lng cng sut

cn pht trn ng ln da trn cc tnh ton tn hao ng truyn trn ng xung

v t s tn hiu trn nhiu yu cu.

3.4.4 iu khin cng sut ng xung (t BTS n MS)


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-iu khin cng sut c thc hin trn knh TCH v SDCCH (bt tham sSDCCHREG).

-Ton b TSs trn knh BCCH c pht vi cng sut ti a v khng c iukhin cng sut trn cc knh ny.

-REGINDL: l thi gian gia 2 ln iu chnh cng sut n v l chu kkhung SACCH (n*480 (ms)) (Hin ti trong mng viettel th n = 1).

Tng quan gia suy hao (path loss) v cng sut pht BTS:

-Cng sut u ra BTS v cng tn hiu trong MS i vi suy hao ngtruyn gia MS v BTS, BTS ch c th truyn ti cc mc cng sut ring bit.

- Khi mt kt ni c tn hao ng truyn thp, BTS truyn ti mc cng sutthp nht c th ca n. Mc d MS nhn c tn hiu vt qu gi tr mong mun,

BTS vn khng th gim cng sut pht thp hn na (min). Ngc li, khi kt ni c

tn hao ng truyn cao (phn bn phi ca hnh), BTS s pht ti mc cng sut ti

a cho php i vi cell. Cng sut pht lc ny khng th tng hn na mc d cng

tn hiu nhn c MS thp (max).

-Vic iu khin y l khng tuyn tnh m theo hnh bc thang.-Mc iu chnh cng sut b gii hn trong khong 0 30dB.-Khi cht lng ca vo tnh ton, cng sutu ra ciu chnh tng

hoc gim ph thuc vo cht lng nhnc. Cng sut trm pht do s thay i

vi cht lng o c bi MS. Khi MS c rxqual thp (cht lng cao), BS pht cng

sut thp v khi MS c rxqual cao, BS pht cng sut cao. Rxqual cng cao th cng

sut pht cng cao v ngc li.

-Nu ch xt trong phm vi 1 cell th cng sut tng ko theo C/I tng, nhngtrong phm vi nhiu cell cnh nhau th cng sut cao s lm tng nhiu do nh hng

gia cc cell xung quanh -> C/I gim.


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3.4.4.1 Thut ton iu khin cng sut BTS

Thut ton iu chnh cng sut BTS ng bao gm 3bc:a. Chun b d liu u vo:

Mc cng sut u ra s dng bi BTS (TRU) ti chu k SACCH th k,c k

hiu bng PLused vi bc nhy 2dB gim dn t mc cng sut u ra t ban u:

BTS (TRU) output power (k) (dBm) = BSPWRT - 2 * PL used

c th s dng cht lng mong mun (QDESDL) v rxqualo c trong

cc tnh ton, c hai phi c chuyn i sang C/I vi n v dB theo bng 3.1. Php

nh x gia rxqual v C/Il khng tuyn tnh do cn s iu chnh nhanh hn cho

cc gi tr rxqualcao v thp.

Mt lng b c tnh ton trc khi lc kt qu o:

- Nu c nhy tn v MS o trn knh BCCH:SSTCH= SSM- (BSPWR-BSTXPWR +2*PL used) /Nf

Trong SSTCHl cng tn hiu trn cc sng mang TCH iu chnh xung,

SSM l cng tn hiu o c bo co bi MS, BSPWR l cng sut u ra ca

BTS trn tn BCCH trong LRP, BSTXPWR l cng sut u ra BTS trn tn TCH

trong LRP, v Nf l s tn s trong chui nhy tn. Tt ccc o c cng tn hiu

c b trc khi lc.

- Tnh ton b cng tnh hiu trong cc trng hp cn li:

Bng 3.2: Mi quan h nh x khng tuyn tnh giarxqualv C/I

QDESDL [dtqu] 0 10 20 30 40 50 60 70Rxqual 0 1 2 3 4 5 6 7

C/I[dB] 23 19 17 15 13 11 8 4


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pu i = i * (SSDESDL- SSFILTERED ) + i * (QDESDL_dB - Q FILTERED )

i = 1, 2

trong i v ic xc nh nh sau:1 = LCOMPDL/ 100 (b suy hao)

1 = QCOMPDL/ 100 (b cht lng)

2 = 0.3 (b suy hao)

2 = 0.4 (b cht lng)

Tham s i and iiu khin vic b suy hao v cht lng. Tham s 1 and 1

c th t bng trung bnh ca LCOMPDL and QCOMPDL trong khi tham s 2

and 2l c nh. Cc gi tr ny c ti u t c mc iu chnh hng ti

nhiu nn thp m khng nh hng cht lng. Tuy nhin vic t 2 and 2 khng

phi l then cht khi cc tham s ny n thun ch cung cp nh mt gii hn cho

vic iu chnh gn ti mc nhiu nn.

Mc cng sut cui cng ny c gi l mc cng sut t nhinpu:

pu = max(pu 1 ,pu 2 ).

c. Chuyn i d liu u ra:

Mc cng sut mi c chuyn i t t l dBm bn trong thnh k hiu PLused

trc khi n c th c truyn ti BTS. Trong thc t iu ny c ngha l mc cng

sut bt buc c quy ra bc tng l 2dB theo:

PLused= Int(-pu/2 ) [0..15]

Trong PLusedl mc cng sut. PLused = 0 ngha l cng sut y v PLused =

15 ngha l iu chnh xung 30dB.

3.4.4.2 Th tc iu chnh

Khi kt ni TCH c thit lp, BTS lun pht cng sut u ra cc i c t

trc, v d trong trng hp sau:


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- Cp pht mt knh TCH.- Cp pht li hoc HO li- HO ni cell v thay i subcell- HO lin cell.Vic iu chnh xung lun lun bt u sau bn tin o c c gi tr u tin.

Thi gian hi p cho vic iu chnh ln c iu khin bi tham s QLENDL v

SSLENDL. QLENDLxc nh thi gian hi p khi nhiu cao v SSLENDL trong

rt do cng tn hiu. Cc gi tr QLENDL and SSLENDL tng ng vi 90%

thi gian tng ca cc b lc hm m.

Thi gian hi p cho vic iu chnh xung c xc nh bi biu thc

QLENDL*UPDWNRATIO /100 v SSLENDL*UPDWNRATIO /100 trong

UPDWNRATIO l t s gia tc iu chnh ln v xung. Cc kt qu ny cho

thy iu chnh ln nhanh v iu chnh xung chm hn.

Khi mt mc cng sut c gi i, n mt khong thi gian l s chu k knh

SACCH REGINTDL trc khi mc cng sut tip theo c th gi. Nu mc cng

sut ny khc vi mc cng sut trc, n s c gi. Nu khng khc, mt mc mi

s c tnh ton theo chu k knh SACCH cho n khi thu c mc cng sut mi

khc vi mc c. Sau mc cng sut mi ny c gi i, v tri qua mt s chu k

knh SACCH REGINTDLtrc khi mc cng sut mi c th c gi li.

3.5 iu khin cng sut trong CDMA IS-95

3.5.1 Scn thit phi iu khin cng sut

CDMA l mt h thng b hn ch ca nhiu giao thoa, v tt cMS u pht

cng tn s. Nhiu giao thoa trong mng ng vai tr rt quan trng xc nh dung

lng ca h thng v cht lng thoi. Cng sut pht t mi MS phi c iu


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khin hn ch nhiu giao thoa. Tuy nhin mc cng sut phi ph hp tha mn

cht lng thoi.

Khi MS chuyn ng, mi trng v tuyn thay i lin tc do pha inh nhanhv chm, che ti, nhiu ngoi v cc yu t khc. Mc tiu ca iu khin cng sut l

gii hn cng sut pht trn ng ln v ng xung trong khi vn duy tr c cht

lng ng truyn mi iu kin. Do tch sng khng nht qun BS, nhiu giao

thoa ng ln nguy him ng xung. V thiu khin cng sut ng ln l

quan trng i vi h thng CDMA v bt buc IS-95.

iu khin cng sut cng c cn c trong cc h thng CDMA gii quyt

hiu ng gn xa. gim thiu hiu ng gn xa, mc ch ca h thng CDMA m

bo rng tt ccc MS t c cng cng sut thu ti cc BS. Gi trch ca cng

sut thu phi l mc ti thiu cn cho php ng truyn p ng cc ch tiu cht

lng do ngi s dng nh ngha (BER, FER, dung lng, tc rt cuc gi v

vng phsng). thc hin chin lc nh vy, cc MS gn BS hn phi pht cng

sut thp hn cc MS xa BS.

Cht lng thoi lin quan n t l li khung (FER) cc ng xung v

ng ln. FER lin quan mt thit vi Eb/It. FER cng ph thuc vo tc t, iu

kin truyn sng a phng v phn b ca cc MS ng knh khc. V FER l so

trc tip ca cht lng tn hiu, cht lng thoi h thng CDMA c o theo

FER ch khng theo Eb/It. Vy m bo cht lng tn hiu tt, ch duy tr Eb/It l

cha , m cn phi p ng c FER. Gii hn cht lng theo khuyn ngh l:

Di FER thng thng: 0.2% n 3% (mc cng sut ti u t c khi FER 1%

di cc ai ca cm li : 3 n khung (gi tr ti u ca cm li t= 2khung).


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3.5.2 iu khin cng sut ng ln

iu khin cng sut ng ln tc ng ln cc knh truy nhp v lu lng. N

c s dng thit lp ng truyn khi khi to cuc gi v phn ng ln cc

thng ging tn ho ng truyn ln. iu khin cng sut ng ln gm iu khin

cng sut vng h(cn gi l iu khin cng sut t qun) v iu khin cng sut

vng kn. iu khin cng sut vng kn gm iu khin cng sut vng trong v iu

khin cng sut vng ngoi.

3.5.2.1 iu khin cng sut vng h(OPC)

OPC hay cn c gi l phng php t iu khin (AGC) my di ng.

Trc khi pht, my di ng gim st tng cng sut thu c t trm gc. Cng sut

o c cho thy tn hao ng truyn i vi tng ngi s dng cn cvo

my di ng iu chnh cng sut pht ca mnh t l nghch vi tng cng sut m n

thu c. iu khin cng sut vng hc th l khng tuyn tnh. Mc ch l cho

php p ng nhanh vi s hiu chnh m nhng p ng chm vi s hiu chnh

dng. Nu cng tn hiu thu c cao c ngha l my di ng rt gn trm gc

hoc lng suy hao ng dn thp th my di ng iu chnh cho cng sut pht

gim xung. Tc tng cng sut pht my di ng thng phi nm trong tc

iu khin cng sut mch vng khp kn t trm gc. Bng cch ny cc my di ng

khng thtng cng sut pht qu ln cho d c s suy gim t ngt cht lng thoi

trn knh hng xung. Nh vy trong phng php ny trm gc khng tham gia voqu trnh iu khin cng sut.

Nhc im ca phng php OPC l do iu kin truyn sng ca ng ln v

xung khc nhau nht l do fading nhanh nn snh gi s thiu chnh xc. Tn s

trung tm ca cc ng ln v xung thng nm cc bng tn khc nhau nn s


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khng c si xng gia hai ng v th tn hao ng truyn gia hai ng l

khc nhau. V d h thng IS-95 hai tn s trung tm cch nhau 45MHz, tn hao

ng truyn hai ng c thkhc nhau n vi dB. h thng CDMA trc yngi ta s dng phng php ny kt hp vi iu khin cng sut vng kn, cn h

thng W-CDMA phng php ny chc s dng thit lp cng sut gn ng

khi truy cp mng ln u tin.

3.5.2.2 iu khin cng sut vng kn

C tht c iu khin cng sut trung bnh thi gian di hiu quhn bng

s iu khin cng sut vng kn nh hnh 3.3. Phng php ny i hi trm gc

phi thng xuyn lin h vi my di ng c ththay i cng sut mt cch thch

ng. BS (hoc MS) thng xuyn c tnh t s tn hiu trn nhiu thu c (SIR) v

so snh n vi t sngng SIRch

. Nu SIRc tnh

cao hn SIRch

th BS (hoc MS)

thit lp bit iu khin cng sut lnh cho MS (hoc BS) h thp cng sut, ngc

li th MS (hoc BS) tng cng sut. Chu k o lnh phn ng ny c thc hin

1500 ln/giy (1,5 KHz) W-CDMA v 8000 ln/giy (8 KHz) CDMA 2000. Tc

ny scao hn mi thay i tn hao ng truyn v thm ch c thnhanh hn

fading nhanh khi MS chuyn ng tc thp. K thut iu khin cng sut vng kn

nh vy c gi l vng trong, cng c s dng cho ng xung mc d y

khng c hin tng gn xa v tt c cc tn hiu n MS trong cng mt u bt u

t mt BS. Tuy nhin, ta vn tin hnh iu khin cng sut y v: khi MS tin dn

n bin gii , n bt u chu nh hng ngy cng tng ca nhiu t cc khc.iu khin cng sut ng xung trong trng hp ny to mt lng d tr cng

sut cho cc MS trong trng hp ni trn. Ngoi ra iu khin cng sut ng xung

cho php bo v cc tn hiu yu do fading Rayleigh gy ra, nht l khi cc m sa li

lm vic khng hiu qu. iu khin cng sut vng ngoi thc hin nh gi di hn


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cht lng ng truyn trn c s t l li khung (FER) hoc t l li bit (BER)

quyt nh SIRch

cho iu khin cng sut vng trong.

Hnh 3.3: Phng php iu khin cng sut vng kn

Tuy nhin vic loi bfading ng ngha vi vic tng cng sut pht v th khi

MS b fading su, cng sut pht s dng ln v nhiu gy ra cho cc cng tng.

iu khin cng sut vng ngoi thc hin iu chnh gi tr SIRch BS (hoc MS)cho ph hp vi yu cu ca tng ng truyn v tuyn t c cht lng cc

ng nh nhau. Cht lng ca cc ng truyn v tuyn thng c nh gi

bng t s bit li hay t s khung li. Mc ch ca vic iu chnh SIRch

nh sau:

Gi s SIR yu cu l FER=1% ph thuc vo tc ca MS v c im tuyn

ng. Nu ta t SIRch

cho trng hp xu nht (cho tc cao nht) th s lng ph

dung lng cho cc kt ni tc thp. Nh vy tt nht l SIRch th ni xungquanh gi tr ti thiu p ng c yu cu cht lng. Hnh 3.4 cho thy sthay i

ca SIRch

theo thi gian. thc hin iu khin cng sut vng ngoi, mi khung s

liu ca ngi s dng c gn ch th cht lng khung CRC. Vic kim tra ch th


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cht lng ny s thng bo cho RNC v vic gim cht lng v RNC s lnh cho BS

tng SIRch

. t iu khin vng ngoi RNC v chc nng ny thc hin sau khi thc

hin kt hp cc tn hiu chuyn giao mm.

Hnh 3.4: iu khin cng sut vng trong v vng ngoi

Cc b gii iu chmi trm gc o t l tn hiu trn tp m ca cc tn hiu

nhn c ca mi my di ng so snh t l ny vi t l tn hiu trn tp m chnh (thng l 0.1dB) v pht cc lnh iu khin ti my di ng qua knh hng i.

C pht 1.25 ms mt ln lnh iu khin u ra c th theo di nhiu Rayleigh trn

knh hng v. N rt quan trng gim thi gian thc hin x l xc nh cng sut

pht v pht lnh mi trng knh khng bthay i nhiu cho ti khi bit iu khin

c nhn my di ng v hot ng iu khin c thc hin thc s.

H thng CDMA cung cp chc nng iu khin cng sut hai chiu (tBS n

my di ng v ngc li) cung cp mt h thng c dung lng ln, cht lngdch v cao v cc li ch khc. B thu CDMA ca BSC chuyn tn hiu CDMA thnh

thng tin sbng hp, khi tn hiu ca cc my di ng khc ch l tn hiu tp m

ca bng rng. Th tc thu hp bng c gi l li x l nhm nng cao t s tn


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hiu/nhiu t gi trm n mt mc ln cho php hot ng vi li bit chp

nhn c.

BS cung cp vic iu khin cng sut t BS ti my di ng nhvic quy nhcng sut ny tng ng vi cng sut o c ti my di ng. Mc ch ca vic

iu khin ny l lm gim cng sut pht ca my di ng khi ri hoc vtr tng

i gn BS lm cho fading a ng thp v gim hiu ng bng rm hay lm gim

nhiu i vi cc BS khc.

ng xung, my thu di ng thu nhiu t cc khc. Vic iu chnh cng

sut l cn thit lm gim mc nhiu m cc my di ng gy ra. Tn ti hai s

iu khin cng sut ng xung:

- Theo khong cch: Khi bit c v tr ca cc my di ng ta c th gim thiu

cng sut pht ca cc my ny bng cch pht i cc mc cng sut ph hp theo

khong cch. Phng php ny ph hp cho mi trng khng b che ti v khi suy

hao cng sut ch ph thuc vo khong cch. Cc my di ng phi o khong cch

n trm gc, trm gc phi pht tn hiu hoa tiu.

- Theo t s C/I (Carrrier to Interferance): Mc ch l lm gim thiu t s C/I

theo yu cu ca ngi s dng. Mun vy mi my di ng phi pht thng tin v C/I

n trm gc v vy trm gc c th quyt nh nn tng hay gim cng sut ca my

di ng .

Trong h thng t bo di tn s dng t trm gc ti my di ng khc vi di

tn tmy di ng ti trm gc. S khc bit tn s ny cho php s dng ng thi

cc my pht v my thu my di ng m khng c hi tip hay nhiu ca cc tn

hiu pht ti my thu. S tch bit tn sny cng c tc dng ln trong x l iu

khin cng sut.

Trong thit k h thng ngi ta mong mun tng ln ti a slng khch hng

gi cng mt lc trong di thng xc nh, ngha l h thng sc dung lng ln.

Dung lng h thng l ti a khi tn hiu truyn ca my di ng c thu bi BS c


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t s S/I mc yu cu ti thiu. Nu tn hiu ca cc my di ng m BS thu c l

qu yu th khng th hy vng cht lng thoi tt v t l li bit qu cao. Nu tn hiu

nhn c trm gc cao th ci thin c cht lng thoi nhng nhiu i vi ccmy di ng khc cng s dng mt knh stng ln lm cho cht lng cuc gi ca

cc thu bao khc b gim nu dung lng ti a khng gim.

3.5.3 iu khin cng sut ng xung

iu khin cng sut ng xung (FLPC: Forward Link Power Control) nhm

gim nhiu giao thoa ng xung. FLPC khng ch hn chnhiu trong m c

bit hiu qu trong vic gim nhiu khc hoc cng khc

H thng CDMA IS-95 c thiu khin cng sut ng xung da trn bo

co v t l li t trm di ng. thc hin iu khin cng sut ng xung,

trm gc nh k gim cng sut pht n trm di ng. Vic gim cng sut ny tip

din n trm di ng yu cu tng cng sut do nhn thy s tng t s li khung

(FER: Frame Error Rate). Lc , trm gc s tng cng sut ln mt bc qui nh

trc (0.5dB chng hn). Tng gim cng sut c thc hin mt ln khung thoi

(15-20ms). Nh vy iu khin cng sut ng xung chm hn iu khin cng

sut ng ln (lnh iu khin cng sut ng ln trong CDMA IS-95 c pht

i 1,25ms mt ln).

V FER c o (khng phi Eb/Itnh iu khin cng sut vng kn), nn qu

trnh ny trc tip phn nh cht lng thoi. Tuy nhin qu trnh ny chm hn nhiu.

V cc m trc giao Walsh c s dng cho ng xung, nn nhiu giao thoa khng

phi vn khn cp. V th o chm khng lm tng ng k gim cht lng h

thng.


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3.6 iu khin cng sut trong h thng thng tin di ng WCDMA/UMTS

3.6.1 Phn loi iu khin cng sut trong h thng WCDMA/UMTS

3.6.1.1 iu khin cng sut cho ng xung v ng ln

iu khin cng sut cho ng ln (t MS n BS) DS-CDMA l mt yu cu

h thng rt quan trng v hiu ng gn-xa. Trong trng hp ny, cn c mt di ng

iu khin khong chng 80 dB. ng xung, khng yu cu iu khin cng

sut trong h thng n t bo, t cc tn hiu c truyn cng nhau v thay i

cng nhau. Tuy nhin trong h thng a t bo, nhiu giao thoa t cc bn cnh lm

gim sc lp t v tr cc cho v do lm gim hiu sut. Nh vy, phi s

dng iu khin cng sut trong trng hp ny lm gim s giao thoa gia cc .

3.6.1.2 iu khin cng sut phn tn v tp trung

Mt biu khin tp trung c tt c cc thng tin v cc kt ni c thit lp

v li knh, v iu khin tt c cc mc cng sut trong mng hay mt phn ca

mng. iu khin cng sut tp trung theo yu cu tn hiu iu khin phm vi rng

trong mng v khng thng dng trong thc t. Chng c th s dng a ra gii

hn v hiu sut ca thut ton phn tn.

Biu khin phn tn chiu khin cng sut ca mt trm pht n v thut

ton ch ph thuc vo ni b, nh SIR hay li knh ca ngi s dng c bit.

Nhng thut ton ny thc hin tt trong trng hp l tng, nhng trong cc h

thng thc t c mt s hiu ng khng thch hp nh :

- Tn hiu o v iu khin lm mt thi gian dn n thi gian tr trong h thng

- Cng sut pht hp l ca my pht b hn ch bi gii hn vt l v s lng

t ha. Nhng hn ch bn ngoi khc nh cng sut pht cc i trn mt knh c

bit tc ng n cng sut ra.


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- Cht lng l mt so c ch quan v cn phi tn dng so c khch

quan hp l.

Hnh 3.5: Phn loi iu khin cng sut

3.6.1.3 Phn loi iu khin cng sut theo phng php o

Theo phng php o, k thut iu khin cng sut c phn thnh 3 loi:

- Trn cscng

- Trn csSIR

- Trn csBER

Trn cscng , cng mt tn hiu n BS t MS c nh gi xc

nh l n cao hn hay thp hn cng mong mun. Sau BS s gi lnh iu

khin cng sut cao hn hay thp hn thch hp.

Trn csSIR, phng php o l SIR khi m tn hiu bao gm nhiu knh v

nhiu gia cc ngi s dng. iu khin cng sut da vo cng d thc hin

hn iu khin cng sut da vo SIR, n phn nh hiu sut s dng h thng tt hn

nh: QoS v dung lng. Mt vn quan trng gn vi iu khin cng sut da vo


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SIR l c kh nng gy hi tip dng lm nguy him n s vng vng ca h thng.

Hi tip dng xut hin trong trng hp khi mt MS di s ch dn ca BS tng

cng sut ca n v iu lp li vi cc MS khc. Trong trng hp c N-MS trongh thng, iu ny lm t lit c N-MS.

Trong iu khin cng sut da vo BER, BER c nh ngha l mt s lng

trung bnh ca cc bit li so vi chui bit chun. Nu cng sut tn hiu v nhiu l

hng s th BER l hm ca SIR, v trong trng hp ny th QoS l tng ng. Tuy

nhin, trong thc t SIR l hm thi gian v nh vy SIR trung bnh s khng tng

ng vi BER trung bnh. Trong trng hp ny, BER l cso t cht lng tt

hn.

3.6.1.4 iu khin cng sut vng kn, iu khin cng sut vng h

Tn ti ba phng php iu khin cng sut sau y:

iu khin cng sut vng h iu khin cng sut nhanh vng kn gm iu khin cng sut vng trong

v iu khin cng sut vng ngoi.

iu khin cng sut vng h thc hin nh gi gn ng cng sut ng

xung ca tn hiu knh hoa tiu da trn tn hao truyn sng ca tn hiu ny. Nhc

im ca phng php ny l do iu kin truyn sng ca ng xung khc vi

ng ln nht l do fading nhanh nn s nh gi s thiu chnh xc. h thng

CDMA trc y, ngi ta s dng phng php ny kt hp vi iu khin cng sut

vng kn, cn h thng WCDMA phng php iu khin cng sut ny chc sdng thit lp cng sut gn ng khi truy cp mng ln u.

Phng php iu khin cng sut nhanh vng kn nh hnh (3.6). phng

php ny BS (hoc MS) thng xuyn c tnh t s tn hiu trn can nhiu thu c

SIR v so snh n vi t s SIR ch (SIR_ch). Nu SIR_c tnh cao hn SIR_ch


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th BS (MS) thit lp bit iu khin cng sut lnh cho MS (BS) h thp cng sut,

tri li n ra lnh MS (BS) tng cng sut. Chu ko-lnh-phn ng ny c thc

hin 1500 ln trong mt giy CDMA2000. Tc ny s cao hn mi s thay itn hao ng truyn v thm ch c th nhanh hn fading nhanh khi MS chuyn ng

tc thp.

Hnh 3.6: Nguyn l iu khin cng sut vng kn

K thut iu khin cng sut vng kn nh vy c gi l vng trong cng

c s dng cho ng xung mc d y khng c hin tng gn xa v tt c cc

tn hiu n cc MS trong cng mt u bt u t mt BS. Tuy nhin l do iu

khin cng sut y nh sau. Khi MS tin n gn bin gii , n bt u chu nh

hng ngy cng tng ca nhiu t cc khc. iu khin cng sut trong trng hp

Gii tri

ph

My thu

Rake

o cht lng

cng sut di

o SIR

So snh vquyt nh

To bt iu khincng sut

SIR ch

So snh vquyt nh

Chtlng ch

Ghp bit iukhin cng sutv lun ht

Vng ngoi

Vng trong

Tn hiubng gc

thu


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ny to mt lng d tr cng sut cho cc MS trong trng hp ni trn. Ngoi ra

iu khin cng sut ng xung cho php bo v cc tn hiu yu do fading Rayleigh

gy ra, nht l khi cc m sa li lm vic khng hiu qu.KCS vng ngoi thc hin nh gi di hn cht lng ng truyn trn cs

t l li FER hoc BER quyt nh SIR ch cho iu khin cng sut vng trong.

Hnh (3.7) cho thy hot ng ca iu khin cng sut ng ln mt knh

fading tc chuyn ng thp ca MS. Cc lnh iu khin cng sut siu khin

cng sut ca MS t l nghch vi cng sut thu c (hay SIR) ti BS. Nhm bo

d tr chnh cng sut theo tng nc, nn ch cn mt lng fading nh v knh tr

thnh knh hu nh khng fading (nhn t pha BS).

Hnh 3.7: iu khin cng sut vng kn b trFadinh nhanh

Tuy nhin vic loi b phading phi tr gi bng tng cng sut pht. V th khi

MS b phading su, cng sut pht s dng ln v nhiu gy ra cho cc khc cng

tng.


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iu khin cng sut vng ngoi thc hin iu chnh gi tr SIRch BS

(MS) cho ph hp vi tng yu cu ca tng ng truyn v tuyn t c cht

lng cc ng truyn v tuyn nh nhau. Cht lng ca cc ng truyn v tuynthng c nh gi bng t s bit li BER hay t s khung li FER (Frame Error

Rate). L do cn t li SIRch nh sau : SIR yu cu (t l vi Eb/No) chng hn l

FER=1% ph thuc vo tc ca MS v c im truyn nhiu ng. Nu ta t

SIRch cho trng hp xu nht (cho tc cao nht) th s lng ph dung lng cho

cc kt ni tc thp. Nh vy, tt nht l SIRch th ni xung quanh gi tr ti

thiu p ng c yu cu cht lng. Hnh (3.8) cho thy s thay i SIRch theo

thi gian

Hnh 3.8: iu khin cng sut vng ngoi

thc hin iu khin cng sut vng ngoi, mi khung s liu ca ngi s dng

c gn ch th cht lng khung l CRC. Vic kim tra ch th cht lng ny s

MS khngchuyn ng

SIR ch

Thi gian (s)


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thng bo cho RNC v vic gim cht lng v RNC s lnh cho BS tng SIRch. L

do t iu khin vng ngoi RNC v chc nng ny thc hin sau khi thc hin kt

hp cc tn hiu chuyn giao mm.

3.6.2 iu khin cng sut vng htrong WCDMA/UMTS

iu khin cng sut vng hc s dng trong UMTS FDD cho vic thit lp

nng lng ban u cho MS. Trm di ng stnh ton suy hao ng truyn gia cc

trm gc v trm di ng bng cch o cng tn hiu nhn s dng mch iu

khin tng ch t ng (AGC). Ty theo s tnh ton suy hao ng truyn ny,

trm di ng c th quyt nh cng sut pht ng ln ca n. iu khin cng sut

vng hc nh hng trong h thng TDD bi b ng ln v ng xung l tng

h, nhng khng nh hng nhiu trong cc h thng FDD bi v cc knh ng ln

v ng xung hot ng trn cc bng tn khc nhau v hin tng Fadinh Rayleigh

trn ng ln v ng xung c lp nhau. Vy iu khin cng sut vng hch c

th b mt cch i khi suy hao do khong cch. l l do ti sao iu khin cng

sut vng hchc s dng nh l vic thit lp nng lng ban u trong h thng

FDD.

3.6.2.1 Th tc truy nhp ngu nhin RACH v truy nhp gi CPCH

Do KCS hp dng cho cc knh chung: RACH v CPCH nn ta s xt th tc

truy nhp ca cc knh RACH v CPCH ny.


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Hnh 3.9: Th tc truy cp ngu nhin v truy cp gi

Th tc truy nhp ngu nhin RACH: Theo hnh 3.9a UE khi xng th tc truy

nhp ngu nhin RACH bng cchpht i mt AP (tin truy t nhp). Nu chp nhn

(OK), nt B pht AICH (ch th pht hin bt) n UE. Sau UE c th pht bn tin

trn knh RACH (knh truy nhp ngu nhin) thng qua knh RACH.

Th tc truy nhp gi CPCH: Nh trn hnh 3.9b, da trn thng tin kh dng

ca tng knh PCPCH do CSICH (Knh ch th trng thi CPCH) thng bo, UE khi


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xng th tc truy nhp CPCH trn knh cha s dng bng cch pht i mt AP (tin

t truy nhp). Nu c nt B chp nhn (OK) UE pht i mt CD (tin t pht hin va

chm) thng bo rng n chim knh ny. Cui cng nt B pht i CD/CA-ICH(ch th pht hin va chm v n nh knh) n UE. Sau UE c th pht gi trn

knh CPCH (knh gi chung) thng qua PCPCH.

Knh RACH (Random Access Channel Knh truy cp ngu nhin): L knh

truyn ti, l knh chung ng ln pht thng tin iu khin v s liu ngi s

dng, p dng trong truy nhp ngu nhin v c s dng truyn s liu thp ca

ngi s dng.

Knh CPCH (Common Packet ChannelKnh gi chung): L knh truyn ti, l

knh chung ng ln pht thng tin iu khin v s liu ngi s dng, p dng

trong truy nhp ngu nhin v c s dng truyn s liu thp ca ngi s dng.

Knh CPCH (Common Packet Channel Knh gi chung): Knh chung ng

ln pht s liu ngi s dng, p dng trong truy nhp ngu nhin v c s dng

trc ht truyn s liu cm.

Cc knh truyn ti c chuyn thnh cc knh vt l.


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Hnh 3.10: Chuyn i gia knh truyn ti v knh vt l

RACH==> PRACH (Knh vy l truy cp ngu nhin): L knh chung ngln, c s dng mang knh truyn ti RACH.

CPCH ==> PCPCH (Knh vy l gi chung): L knh chung ng ln c s

dng mang knh truyn ti CPCH.

CPCH ==> CPICH (Knh hoa tiu chung): L knh chung ng xung.

Nguyn l ca KCS Vng h


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Hnh 3.11: Nguyn l iu khin cng sut vng h

Trc khi pht: My di ng s tin hnh gim st tng cng sut thu c t

trm gc. Cng sut o c ny s cho thy tn hao ng truyn i vi tng ngi

s dng. Cn cvo MS iu chnh cng sut pht ca mnh t l nghch vi tng

cng sut m n thu c.Nu cng tn hiu thu c cao c ngha l MS gn trm gc hoc lng suy

hao ng truyn thp. MS iu chnh cho cng sut pht gim xung. Tc tng

cng sut pht ca MS thng c phi nm trong tc iu khin cng sut mch

vng khp knh t trm gc.

Yu cu v mt chnh xc trong KCS vng htrong khong 9 dB iu kin

bnh thng.


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3.6.2.2 Cu trc knh vt l ng ln v ng xung

Hinh 3.12: Cu trc knh vt l ng ln v ng xung

Do KCS vng kn v hu p dung cho cc knh ring c th l knh DPDCH

v knh DPCCH nn ta si tm hiu v cu trc knh vt l ng ln v ng

xung:

Cu trc knh vt l ring c trnh by trn hnh 3.12. Trong m hnh nymi cp hai bit th hin mt cp I/Q (mt k hiu) ca ch QPSK. T hnh v ta

thy, cu trc khung bao gm mt chui cc khung v tuyn, mi khung bao gm 15

khe (di 10ms, cha 38400 chip) v mi khe cha 2560 chip (di 0.667 ms) bng mt

chu k KCS (tn sKCS l 1500 ln trong mt giy

Cu trc knh vt l ring ng ln cho mt khe (mt chu kiu khin cngsut) c cho trn hnh hnh 3.12. Thng tin ring lp cao hn gm s liu ngi s


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dng v bo hiu c mang bi DPDCH ng ln v thng tin iu khin to

ralopws 1 c mang bi DPCCH. DPCCH bao gm cc k hiu hoa tiu quy nh

trc (c s dng c tnh knh v tch sng nht qun), cc lnh KCS (TPC:Transmit Power Control), thng tin phn hi (FBI: Feedback Informatinon) cho phn

tp pht vng kn v k thut phn tp chn trm (SSDT: Site Selection Diversity

Technique), TFCI (ty chn). C th khng c, mt hay mt s (nhiu nht l 6) knh

DPDCH trn mt lin kt v tuyn, nhng ch c mt DPCCH cho lin kt ny.

DPDCH (hoc cc DPDCH) v DPCCH c ghp chung theo m I/Q ngu nhin ha

phc.

Cu trc knh vy l ring ng xung c m t hnh 3.12. Trn ngxung knh ring (DPCH) ng xung bao gm DPDCH ng xung v DPCCH

ng xung ghp theo thi gian vi ngu nhin ha phc. S liu ring c to ra ti

cc mc cao hn trn DPDCH c php theo thi gian vi cc bt hoa tiu, cc lnh

TPC v cc bit TFCI (ty chn) c to ra ti lp vt l.

3.6.2.3 K thut iu khin cng sut vng hng ln

Chc nng PC (Power Control) c thc hin cu cui v UTRAN. Chc

nng ny i hi mt s thng siu khin c pht qung b trong v cng sut

m tn hiu thu c RSPC (Received Signal Code Power) c o ti UE trn P-

CPICH tch cc. Da trn tnh ton vng h, UE thit lp cc cng sut khi u trn

tin t PRACH v cho DPCCH ng ln trc khi khi u PC vng trong. Trong

th tc truy cp ngu nhin, cng sut ca AP u tin c thit lp bi UE nh sau :

Preamble_Initial_Power = CPICH_Tx_powerCPICH_RSCP (3.1)

+ UL_interference +UL_required_CI

Trong cng sut P_CPICH (CPICH_Tx_Power) v C/I yu cu ng ln

(UL_required_CI) (trong 3GPP c nh ngha l gi tr khng i khi thit lp quy


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hoch v tuyn) v nhiu ng ln (UL_interference) (trong 3GPP l tng cng sut

bng rng ti my thu) c o ti Node B v c truyn qung b trn BCH. UE

cng s tin hnh th tc khi lp mc cng sut ban u cho CD-AP.Khi tnh ton DPCCH u tin, UE khi u PC vng trong ti cng sut nh

sau :

DPCCH_Initial_power = DPCCH_Power_offsetCPICH_RSCP

(3.2)

Trong cng sut m tn hiu thu ca P_CPICH (CPICH_RSCP) c o ti

UE v dch cng sut DPCCH (DPCCH_Power_offset) c tnh ton bi iu khin

cho php AC trong RNC v c cung cp cho UE khi kt ni RRC hay trong qu

trnh vt mang v tuyn hay khi lp li cu hnh knh vt l nh sau :

DPCCH_Power_offset = CPICH_Tx_power + UL_interference + SIRDPCCH

+10lg(SFDPDCH) (3.3)

Trong SIRDPCCH l SIR ch khi u do AC to ra i kt ni c th ny l

SFDPCCH l h s tri phi vi DPDCH tng ng.

3.6.2.4 K thut iu khin cng sut vng hng xung

Trn ng xung, PC vng h thit lp cng sut khi u cc knh ng

xung trn csbo co o t t UE. Chc nng ny c thc hin cUE v

UTRAN. Gii thut tnh ton gi tr cng sut khi uDPCCH khi dch v mang

u tin c thit lp nh sau :

PTxIntinial PtxTotalNoEb powerTxCPICHWNoEbRb CPICHDL

./

__)/.(

(3.4)

Trong Rb l tc bit ca ngi s dng, (Eb/No)DL l gi trc quy

hoch ca ng xung trong qu trnh quy hoch mng v tuyn i vi vt mang c

th ny, W l tc chip, (Eb/No)CPICH c bo co t UE, PtxTotal l cng sut


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sng mang ti Node B c bo co cho RNC. Gii thut tnh ton cng sut on ni

v tuyn khi u c thc n gin ha khi chuyn giao c thit lp hay on

ni v tuyn thay i. Khi b sung nhnh, cn chnh cli cng sut m pht caon ni hin c bng hiu s gia cng sut P_CPICH ca hin thi vi cng sut

P_CPICH ca thuc nhnh b sung. i vi knh mang thay i nh cc thc

hin bng tc bit ca ngi s dng mi v Eb/No ng xung mi.

3.6.3 iu khin cng sut cc knh chung ng xung

Cng sut truyn dn cc knh chung ng xung c xc nh bi mng.

Ni chung t l gia cng sut pht ca knh chung ng xung khc nhau khng

c c t trong 3GPP v thm ch c th thay i linh hot. Cc mc cng sut knh

chung c cho bng 3.3.


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Bng 3.3: Cc mc cng sut knh chung ng xung in hnh

Knh chung ngxung

Mc cng su tin hnh

Lu

P-CPICH

P-SCH v S-SCH

P-CCPCH

PICH

AICH

A-CCPCH

3033 dBm

-3 dB

-5 dB

-8 dB

-8 dB

-5dB

210% cng su t pht cc i ca (20 W)

So vi cng sut P-CPICH

So vi cng sut P-CPICH

So vi cng sut P-CPICH v N=72

Cng sut ca mt ch th bt (AI) so vi

P-CPICH

So vi cng sut P-CPICH v SF-256 (15 kbps)

Cng sut pht ca P-CPICH, P-SCH, S-SCH, v P-CCPCH l cc thng sc

th c thit lp trong qu trnh quy hoch mng theo kch thc . Thng thng

cng sut P-CPICH bng 5 n 10% tng cng sut pht c th cp pht cho . Cng

sut pht ca cc knh chung khc nhau thit lp tng i so vi cng sut pht ca

P-CPICH.

Cng sut pht ca AICH v PICH l cc thng s cu hnh TrCH chung c

thit lp tng i so vi cng sut pht P-CPICH trong qu trnh quy hoch mng v

tuyn m bo ph ton b . Cc thng s ny c chuyn n Node B mi khi

TrCH chung tng ng c thit lp hay lp li cu hnh.

Cng sut pht PICH ph thuc vo thng s PI trn khung (N). S PI trn khung

cng ln th PI cng c lp nhiu trn khung v cng sut PICH tng i so vi


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P-PICH cng cn cao hn. Gi tr in hnh ca khong dch cng sut l -10 dB

(N=18 hay 36), -8 dB (N=72) v -5 dB (N=144).

Theo tiu chun, khi thit lp hoc lp li cu hnh S-CCPCH (ngha l FACHv PCH), Node B c cung cp thng tin dch cng sut (PO1 cho TFCI), PO3 cho

hoa tiu (hnh 3.12). Trn knh FACH c th p dng PC chm da trn t s Eb/No

ca mt gii thut ring ci thin dung lng ng xung. Trong trng hp ny

gi tr ch th l dch m so vi cng sut cc i c lp cu hnh cho S-CCPCH

mang FACH. Nu ta coi rng cng sut nh nhau i vi tt c TrCH ghp trn cng

knh vt l, cc gi tr cng sut in hnh cho S-CCPCH so vi P-CPICH l +1

i vi SF = 64 (60 kbps), -1dB i vi SF = 128 (30 kbps) v -5 dB i vi SF = 256

(15 kbps). i vi CCPCH, cc gi trin hnh c th l 2 dB cho 15 kbps, 3 dB cho

30 kbps v 4 dB cho 60 kbps. Trong qu trnh thng tin, dch cng sut c th thay i

tu theo tc bit c s dng.

Hnh 3.13: Cng sut pht trin knh S-CCPCH, PO3 v PO1 k hiu cho dch

3.6.4 Cc th tc iu khin cng sut vng trong

iu khin cng sut vng trong (iu khin cng sut nhanh) da trn thng tin

hi tip lp 1 tu kia ca ng truyn v tuyn. Thng tin ny cho php UE/Node

TFCIS liu

Hoa tiu

TS = 2560 chip

PO1

PO3


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B iu chnh cng sut pht ca mnh da trn mc SIR thu c b tr fading ca

knh v tuyn. Chc nng iu khin cng sut vng htrong UMTS c s dng

cho cc knh ring cng ln v ng xung v i vi CPCH chng ln.Trong WCDMA, PC nhanh c thc hin tn s 1,5 kHz.Tng quan cc th tc

iu khin cng sut vng trong c cho hnh (3.14).

3.6.4.1 iu khin cng sut vng trong ng ln

iu khin cng sut vng trong ng ln c s dng thit lp cng sut

DPCH v CPCH ng ln. Node B nhn c SIR ch t UL PC vng ngoi RNC

v so snh n vi SIR c tnh trn k hiu hoa tiu ca DPCCH ng ln trong tng

khe. Nu SIR thu c ln hn SIR ch, Node B pht lnh h thp n UE, ngc

li Node B pht lnhtng thmn UE trn DPCCH ng xung.

Kch thc bc PC theo tiu chun ph thuc vo tc UE. i vi ch cht

lng cho trc, kch thc bc UL PC tt nht l kch thc cho SIR ch nh nht.

Vi tc iu khin cng sut 1500 Hz, kch thc bc PC 1dB c th theo kp

knh phading Raleigh vi tn s ln n 55 Hz (30 Km/h).Ti tc cao hn (ti 80

Km/h) kch thc bc PC 2dB s tt hn. Ti tc cao hn 80 Km/h, iu khin

cng sut vng trong khng theo kp phading v v th tp m vo ng dn ng

ln. C th gim nh hng xu ny bng cch s dng bc PC nh hn 1 dB. Ngoi

ra i vi tc UE thp hn 3 Km/h, khi tn sut phading knh rt nh, s dng bc

PC nh c li hn.

Hai gii thut (gii thut 1 v 2) c c t cho UE din gii cc lnh TPC t

Node B. Gii thut 1 s dng khi tc UE thp b tr phading knh. Bc PC

c thit lp trong qu trnh quy hoch mng v tuyn l 1 n 2dB. Gii thut 2

c thit k m phng nh hng khi s dng bc nh hn 1 dB v c th s

dng b tr xu th phading chm ca knh truyn sng. N hot ng tt hn gii


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thut 1 khi UE chuyn ng nhanh hn 80 Km/h v chm hn 3 Km/h. Trong gii

thut bc PC cnh bng 1 dB. UE khng thay i cng sut pht cho n khi nhn

c lnh TCP tip theo. Ti cui khe th 5, da trn quyt nh cng, UE iu chnhcng sut theo quy tc nh sau :

Nu tt c 5 lnh TPC l gim, cng sut gim 1 dBNu tt c 5 lnh TPC l tng, cng sut pht tng 1 dBTri li cng sut pht khng iTrc khi khi u UL DPDCH, UE c thc mng hng dn s dng tin

t UL DPDCH, PC khi nhn c DPDCH ng xung. di ca tin t DPDCH

PC l mt thng sc thit lp khi quy hoch mng v tuyn trong di t 0 n 7

khung. Trong tin t UL DPDCH PC, cc lnh TPC do Node B pht lun tun theo gii

thut 1 m bo t cng sut pht ng ln nhanh hn trc khi bt u iu

khin cng sut thng thng.

Trong UMTS, cc s phn tp ch p dng cho cc knh ring. Sau khi t

c ng b lp 1, mt hay nhiu tham gia vo chuyn giao phn tp s bt u PC

vng trong ng ln. Mi trong s cc ni n UE so SIR ng ln v so snh

SIR c tnh vi SIR ch to ra lnh TPC gi n UE. Nu tt c cc u yu cu

tng cng sut th UE mi tng cng sut.


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Hnh 3.14:UL PC vng trong khi chuyn giao mm

Khi UE chuyn giao HO (Hand Over) mm, Node B phc v s thng bo cho

UE n kt hp cc lnh TPC n t cng mt tp on ni v tuyn vo mt lnh

TPC theo gii thut 2 hoc 1. Cc th tc kt hp cc lnh TPC t cc on ni v

tuyn trong HO mm c minh ha hnh (3.15).

Nu cc lnh TPC n t cc khc nhau v gii thut 1 c s dng, th UE rt

ra mt lnh TPC kt hp trn c s quyt nh mm v thay i cng sut pht ca

mnh theo bc PC quy nh trc. Nu gii thut 2 c s dng, th UE thc hin

quyt nh cng theo gi tr ca tng lnh TPC tcc on v tuyn khc nhau cho

nm khe lin tip sau ng chnh. Sau UE rt ra lnh TPC cho khe thnm theonguyn tc sau:

Nu gi tr trung bnh ca cc c tnh lnh TPC tc thi ln hn 0,5, tng cngsut 1 dB

SRNC

Node B1 Node B2

Nhnh chnh Nhnh b sungMDC v phn chia

UL PC vng ngoi

+SIR=f(BLER orBER)

TPC1 TPC2

UE

Iub Iub

RAKE MDC (cc k hiu sliu v hoa tiu)

SIR1 so vi SIR ch -> cc Gii thut 1 hay 2 kt hpTCP1 v TCP2 thnh TCP

RAKE MDC (cc k hius liu v hoa tiu )

SIR1 so vi SIR ch->

MDC : Macro Diversity Combiner = b kt hp phn tp v m.

UuUu


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Nu gi tr trung bnh ca cc c tnh lnh TPC tc thi nh hn 0,5, gimcng sut 1 dB

Tri li khng thay i cng sutTrong tnh ton ng ln, lnh tng c th hin bng gi tr+1 cn lnh

gim bng gi tr-1.

Trong qu trnh kt hp, sau khi p dng iu chnh cng sut DPCH, tiu chun

yu cu UE phi c kh nng gim cng sut pht ca mnh t nht n -50 dBm. Gi

s cng sut pht cc i ca UE l 21 dBm (250 mW), ta c di ng iu khin

cng sut vo khong 70 dB.

3.6.4.2 iu khin cng sut vng trong ng xung

UE nhn BLER ch do RNC thit lp cho DL PC vng ngoi cng vi cc thng

siu khin khc. UE so snh SIR c tnh vi SIR ch. Nu c tnh ln hn ch,

UE pht lnh TPC gim n Node B, ngc li n pht lnh TPC tng n Node B

Hnh 3.15:Dch cng sut (PO) ci thin cht lng bo hiu ng xung

S liu 1

TPC TFC1 S liu 2Hoa tiu

DPDCH DPCCH DPDCH DPCCH

Thi gian (s)

DL DPCH

Cng sutpht ngxung (w)

TS = 256 chip

PO2

PO1PO3


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Nu DPC_MODE = 0 UE pht mt lnh TPC cho mi khe, tri li n pht mt

lnh TPC cho ba khe. Cc lnh TPC c pht trn UL DPCCH iu khin cng

sut ca DL DPDCH v cc DPDCH tng ng vi n bng cng mt lng cngsut. Dch cng sut ca cc k hiu TFCI (PO1), TPC (PO2) v hoa tiu (PO3) ca

knh DL DPCCH so vi knh DL DPDCH c cho hnh (3.15).

Kch thc bc DL PC l mt thng s ca qu trnh quy hoch mng v tuyn

cc bc c th l 0,5; 1; 1,5 hoc 2 dB. Bc bt buc ti thiu l 1dB cn cc bc

khc l tu chn. Nu UE chuyn giao mm SHO (Soft Hand Over), tt c cc ni

n UE phi c bc PC nh nhau trnh tri cng sut. Trong trng hp nghn,

RNC c th lnh cho Node B khng thc hin lnh TPC tng ca UE.

Hnh 3.16:. Di ng iu khin cng sut ng xung

DL PC vng trong trong qu trnh HO mm hn hot ng ging nh trong

trng hp on ni v tuyn. Ch c mt DPCCH c pht ng ln, bo hiu v


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RNC do tr qu ln v bo hiu qu nhiu trong mng. Do li bo hiu nn cc Node B

c th gii lnh iu khin cng sut theo cc cch khc nhau. Nn c th mt Node B

h thp cng sut pht ca mnh trong khi Node B khc li tng cng sut pht. iuny dn n cng sut pht xung bt u tri, hin tng ny c gi l tri cng

sut.

Tri cng sut l hin tng khng mong mun, v n gim hiu nng chuyn

giao mm ng xung. Tri cng sut c thc iu khin bi RNC. Phng php

n gin nht l thit lp cc gii hn cht chi vi cc di ng ca iu khin

cng sut. Cc gii hn ny c p dng cho cc cng sut pht c th ca MS. Tt

nhin di ng cng nh th tri cng sut cc i cng t. Tuy nhin iu ny lm

gim li nhn c t SHO.

C mt cch khc gim tri cng sut nh sau. RNC c th nhn thng tin t

cc Node B lin quan n cc mc cng sut pht ca cc kt ni chuyn giao mm.

Cc mc ny c trung bnh ho trn mt s lnh iu khin cng sut, chng hn

trong 500 ms hay tng ng vi 750 lnh iu khin cng sut. Trn cscc kt

quo ny RNC c th pht gi tr tham chun cho cc cng sut pht Pref n cc

Node B. Cc Node B trong SHO s dng gi tr tham kho ny iu khin cng sut

ca chng cho kt ni v gim tri cng sut. tng y l mt hiu chnh nh

c thc hin nh k cho cng sut tham chun. Tri cng sut ch xy ra khi c iu

khin cng sut nhanh ng xung. IS-95 ch c iu khin cng sut chm ng

xung v khng cn phng php iu khin tri cng sut.

3.6.5 iu khin cng sut vng ngoi

Mc ch ca gii thut iu khin cng sut vng ng

do an full

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